Veracyte (VCYT) 10-K 1 Mar 17 2016 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Feb. 24, 2017	Jun. 30, 2016
Document and Entity Information
Entity Registrant Name	VERACYTE, INC.
Entity Central Index Key	1,384,101
Document Type	10-K
Document Period End Date	Dec. 31, 2016
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Entity Public Float			$ 87.5
Entity Common Stock, Shares Outstanding		33,848,284
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	FY

Balance Sheets

Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 59,219	$ 39,084
Accounts receivable	8,756	3,503
Supplies inventory	3,475	3,767
Prepaid expenses and other current assets	2,057	1,442
Restricted cash	120	118
Total current assets	73,627	47,914
Property and equipment, net	11,480	10,314
Finite-lived intangible assets, net	14,133	15,200
Goodwill	1,057	1,057
Restricted cash	603	603
Other assets	134	159
Total assets	101,034	75,247
Current liabilities:
Accounts payable	2,424	5,085
Accrued liabilities	9,110	8,689
Deferred Genzyme co-promotion fee	0	948
Total current liabilities	11,534	14,722
Long-term debt	24,918	4,990
Capital lease liability, net of current portion	599	0
Deferred rent, net of current portion	4,402	4,283
Total liabilities	41,453	23,995
Commitments and contingencies
Stockholders' equity:
Preferred stock, $0.001 par value; 5,000,000 shares authorized, no shares issued and outstanding as of December 31, 2016 and 2015	0	0
Common stock, $0.001 par value; 125,000,000 shares authorized, 33,762,278 and 27,685,291 shares issued and outstanding as of December 31, 2016 and 2015, respectively	34	28
Additional paid-in capital	239,631	199,950
Accumulated deficit	(180,084)	(148,726)
Total stockholders' equity	59,581	51,252
Total liabilities and stockholders' equity	$ 101,034	$ 75,247

Balance Sheets (Parenthetical)

Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized	125,000,000	125,000,000
Common stock, shares issued	33,762,278	27,685,291
Common stock, shares outstanding	33,762,278	27,685,291

Statements of Operations and Co

Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Statement [Abstract]
Revenue	$ 65,085	$ 49,503	$ 38,190
Operating Expenses:
Cost of revenue	25,462	21,497	16,606
Research and development	15,324	12,796	9,804
Selling and marketing	28,248	25,293	21,932
General and administrative	23,787	22,583	18,854
Intangible asset amortization	1,067	800	0
Total operating expenses	93,888	82,969	67,196
Loss from operations	(28,803)	(33,466)	(29,006)
Interest expense	(2,757)	(378)	(439)
Other income, net	202	140	72
Net loss	(31,358)	(33,704)	(29,373)
Comprehensive loss	$ (31,358)	$ (33,704)	$ (29,373)
Net loss per common share, basic and diluted (in dollars per share)	$ (1.09)	$ (1.30)	$ (1.36)
Shares use to compute net loss per common share, basic and diluted (in shares)	28,830,472	25,994,193	21,639,374

Statements of Stockholders' Equ

Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Deficit
Balance at Dec. 31, 2013	$ 56,443	$ 21	$ 142,071	$ (85,649)
Balance (in shares) at Dec. 31, 2013		21,143,313
Increase (Decrease) in Convertible Preferred Stock and Stockholders' Equity (Deficit)
Issuance of common stock on exercise of stock options	675	$ 1	674
Issuance of common stock on exercise of stock options (in shares)		402,100
Issuance of common stock on cashless exercise of warrant (in shares)		13,739
Common stock subject to repurchase	3		3
Issuance of common stock for acquisition	10,078	$ 1	10,077
Issuance of common stock for acquisition (in shares)		964,377
Stock-based compensation expense (employee)	3,388		3,388
Stock-based compensation expense (non-employee)	160		160
Net loss	(29,373)			(29,373)
Comprehensive loss	(29,373)			(29,373)
Balance at Dec. 31, 2014	41,374	$ 23	156,373	(115,022)
Balance (in shares) at Dec. 31, 2014		22,523,529
Increase (Decrease) in Convertible Preferred Stock and Stockholders' Equity (Deficit)
Issuance of common stock on exercise of stock options	722		722
Issuance of common stock on exercise of stock options (in shares)		253,787
Issuance of common stock for acquisition	0
Sale of common stock in a private placement, net of issuance costs	37,258	$ 5	37,253
Sale of common stock in a private placement, net of issuance costs (in shares)		4,907,975
Issuance of common stock in a private placement, issuance cost	2,742
Stock-based compensation expense (employee)	5,302		5,302
Stock-based compensation expense (non-employee)	110		110
Stock-based compensation expense (ESPP)	190		190
Net loss	(33,704)			(33,704)
Comprehensive loss	(33,704)			(33,704)
Balance at Dec. 31, 2015	51,252	$ 28	199,950	(148,726)
Balance (in shares) at Dec. 31, 2015		27,685,291
Increase (Decrease) in Convertible Preferred Stock and Stockholders' Equity (Deficit)
Issuance of common stock on exercise of stock options	$ 538		538
Issuance of common stock on exercise of stock options (in shares)	212,740	212,740
Issuance of common stock under employee stock purchase plan (ESPP)	$ 678		678
Issuance of common stock on employee stock purchase plan (ESPP) (in shares)		140,947
Issuance of common stock for acquisition	0
Sale of common stock in a private placement, net of issuance costs	32,093	$ 6	32,087
Sale of common stock in a private placement, net of issuance costs (in shares)		5,723,300
Issuance of common stock in a private placement, issuance cost	2,247
Stock-based compensation expense (employee)	6,046		6,046
Stock-based compensation expense (non-employee)	15		15
Stock-based compensation expense (ESPP)	317		317
Net loss	(31,358)			(31,358)
Comprehensive loss	(31,358)			(31,358)
Balance at Dec. 31, 2016	$ 59,581	$ 34	$ 239,631	$ (180,084)
Balance (in shares) at Dec. 31, 2016		33,762,278

Statements of Cash Flows

Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating activities
Net loss	$ (31,358)	$ (33,704)	$ (29,373)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	3,511	2,254	1,175
Bad debt expense	68	105	54
Loss on disposal of property and equipment	12	0	0
Genzyme co-promotion fee amortization	(948)	(1,897)	(2,269)
Stock-based compensation	6,378	5,602	3,548
Conversion of accrued interest to long-term debt	385	0	0
Amortization of debt discount and issuance costs	173	46	97
Interest on debt balloon payment and prepayment penalty	206	79	81
Changes in operating assets and liabilities:
Accounts receivable	(5,321)	(558)	(1,961)
Supplies inventory	292	(71)	(1,129)
Prepaid expenses and current other assets	(415)	304	(38)
Other assets	25	(42)	(46)
Accounts payable	(1,441)	(3,546)	1,874
Accrued liabilities and deferred rent	451	4,463	355
Net cash used in operating activities	(27,982)	(26,965)	(27,632)
Investing activities
Purchases of property and equipment	(4,210)	(6,165)	(2,024)
Cash remitted for acquisition, net of cash received	0	0	(6,916)
Change in restricted cash	(2)	(533)	(70)
Net cash used in investing activities	(4,212)	(6,698)	(9,010)
Financing activities
Proceeds from the issuance of long-term debt, net of debt issuance costs	24,452	0	0
Proceeds from issuance of common stock in a private placement, net of issuance costs	0	37,258	0
Proceeds from issuance of common stock in a public offering, net of issuance costs	31,949
Commissions and issuance costs relating to initial public offering	0	0	(129)
Payment of long-term debt	(5,000)	0	0
Payment of end-of-term debt obligation and prepayment penalty	(288)	0	(110)
Payment of deferred stock offering costs	0	(247)	0
Proceeds from the exercise of common stock options and employee stock purchases	1,216	722	675
Net cash provided by financing activities	52,329	37,733	436
Net increase (decrease) in cash and cash equivalents	20,135	4,070	(36,206)
Cash and cash equivalents at beginning of period	39,084	35,014	71,220
Cash and cash equivalents at end of period	59,219	39,084	35,014
Supplementary cash flow information of non-cash investing and financing activities:
Fair value of common stock issued for acquisition	0	0	10,078
Non-cash issuance of long-term debt	0	0	5,000
Non-cash repayment of long-term debt	0	0	(5,000)
Net receivable for reimbursement of public offering issuance costs	144	0	0
Purchases of property and equipment included in accounts payable and accrued liabilities	363	1,825	383
Issuance of common stock from the non-cash exercise of common stock warrants	0	0	187
Supplementary cash flow information:
Cash paid for interest on debt	2,149	278	307
Cash paid for tax	$ 7	$ 22	$ 0

Organization and Description of

Organization and Description of Business	12 Months Ended
	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Description of Business	Organization and Description of Business Veracyte, Inc. ("Veracyte" or the "Company") was incorporated in the state of Delaware on August 15, 2006 as Calderome, Inc. Calderome operated as an incubator until early 2008. On March 4, 2008, the Company changed its name to Veracyte, Inc. Veracyte is a molecular diagnostics company that uses genomic technology to resolve diagnostic ambiguity. The Company targets diseases in which large numbers of patients undergo invasive and costly diagnostic procedures that could have been avoided with a more accurate diagnosis from a cytology sample. By improving diagnosis, the Company helps patients avoid such unnecessary invasive procedures and surgeries while reducing healthcare costs. The Company's first commercial solution, the Afirma® Thyroid FNA Analysis, centers on the proprietary Afirma Gene Expression Classifier ("GEC"). The Afirma GEC helps physicians reduce the number of unnecessary surgeries by employing a proprietary 142-gene signature to determine whether thyroid nodules previously classified by cytopathology as indeterminate can be reclassified as benign. The Afirma GEC is offered directly or as part of a comprehensive solution that also includes cytopathology. Additionally, the Afirma Malignancy Classifiers were launched in May 2014. The Company currently markets and sells Afirma in the United States, in select foreign countries through a co-promotion agreement with Genzyme Corporation, a subsidiary of Sanofi, and through other distributors. In April 2015, the Company entered the lung cancer diagnostics market with the Percepta® Bronchial Genomic Classifier, a genomic test to resolve ambiguity in lung cancer diagnosis. In October 2016, the Company introduced a second product in pulmonology, the Envisia ™ Genomic Classifier, designed to help in the assessment of patients suspected to have idiopathic pulmonary fibrosis. The Company's operations are based in South San Francisco, California and Austin, Texas, and it operates in one segment in the United States.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2016
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Basis of Presentation The Company's financial statements have been prepared in accordance with accounting principles generally accepted in the United States ("GAAP"). The financial statements include the accounts of the Company and its former wholly-owned subsidiary, which was dissolved in June 2015. For periods prior to the subsidiary dissolution, all intercompany accounts and transactions were eliminated in consolidation. Certain amounts have been reclassified on the balance sheet at December 31, 2015 to conform with the adoption of Accounting Standards Update (“ASU”) No. 2015-3, Simplifying the Presentation of Debt Issuance Costs. Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities as of the date of the financial statements and the reported amounts of revenue and expenses during the reporting period. Significant items subject to such estimates include: revenue recognition; contractual allowances; the useful lives of property and equipment; the recoverability of long-lived assets; the estimation of the fair value of intangible assets; stock options; income tax uncertainties, including a valuation allowance for deferred tax assets; and contingencies. The Company bases these estimates on historical and anticipated results, trends, and various other assumptions that the Company believes are reasonable under the circumstances, including assumptions as to future events. These estimates form the basis for making judgments about the carrying values of assets and liabilities and recorded revenue and expenses that are not readily apparent from other sources. Actual results could differ from those estimates and assumptions. Liquidity The Company has incurred net losses since its inception and expects to incur additional losses in 2017 and in future years. As of December 31, 2016 , the Company had an accumulated deficit of $180.1 million . The Company may never achieve revenue sufficient to offset its expenses. The Company believes its cash and cash equivalents of $59.2 million as of December 31, 2016 and its revenue from sales in 2017 will be sufficient to meet its anticipated cash requirements for at least the next 12 months. In November 2016, the Company issued and sold 5,723,300 shares of its common stock in a public offering, at a price of $6.00 per share. The Company raised $32.1 million in net proceeds, after deducting expenses of $2.2 million . In March 2016, the Company entered into a credit agreement and drew down the initial $25.0 million term loan of which, $5.0 million was used to pay the outstanding balance of the Company’s existing long-term debt as discussed in Note 8 - Debt. In April 2015, the Company issued and sold 4,907,975 shares of its common stock in a private placement, at a price of $8.15 per share. The Company received $37.3 million in net proceeds, after deducting expenses of $2.7 million . If the Company is not able to generate revenue to finance its cash requirements, the Company will need to finance future cash needs primarily through public or private equity offerings, debt financings, borrowings or strategic collaborations or licensing arrangements. If the Company is not able to secure additional funding when needed, on acceptable terms, it may have to delay, reduce the scope of or eliminate one or more research and development programs or selling and marketing initiatives which may have a material adverse effect on the Company's business, results of operations, financial condition and/or its ability to fund its scheduled obligations on a timely basis or at all. Concentrations of Credit Risk and Other Risks and Uncertainties The majority of the Company's cash and cash equivalents are deposited with one major financial institution in the United States. Deposits in this institution may exceed the amount of insurance provided on such deposits. The Company has not experienced any losses on its deposits of cash and cash equivalents. Several of the components of the Company's sample collection kit and test reagents are obtained from single-source suppliers. If these single-source suppliers fail to satisfy the Company's requirements on a timely basis, it could suffer delays in being able to deliver its diagnostic solutions, a possible loss of revenue, or incur higher costs, any of which could adversely affect its operating results. The Company is also subject to credit risk from its accounts receivable related to its sales. The Company generally does not perform evaluations of customers' financial condition and generally does not require collateral. Through December 31, 2016 , all of the Company's revenue have been derived from the sale of Afirma. To date, Afirma has been delivered primarily to physicians in the United States. The Company's third-party payers in excess of 10% of revenue and their related revenue as a percentage of total revenue were as follows: Year Ended December 31, 2016 2015 2014 Medicare 27 % 26 % 26 % UnitedHealthcare 12 % 14 % 18 % Aetna 8 % 9 % 11 % 47 % 49 % 55 % The Company's significant third-party payers and their related accounts receivable balance as a percentage of total accounts receivable were as follows: December 31, 2016 2015 Medicare 18 % 31 % UnitedHealthcare 8 % 25 % Aetna 4 % 23 % No other third-party payer represented more than 10% of the Company's accounts receivable balances as of those dates. Cash Equivalents Cash equivalents consist of short-term, highly liquid investments with original maturities of three months or less from the date of purchase. Cash equivalents consist of amounts invested in a money market account primarily consisting of U.S. Treasury reserves. Restricted Cash The Company had deposits of $120,000 and $118,000 as of December 31, 2016 and December 31, 2015 , respectively, included in current assets. The deposit at December 31, 2016 was a pledge for corporate credit cards and the deposit at December 31, 2015 was restricted from withdrawal and held by a bank in the form of collateral for irrevocable standby letters of credit held as security for the lease of the Company's former headquarters and laboratory facilities in South San Francisco that expired March 31, 2016. The Company also had deposits of $603,000 included in long-term assets as of December 31, 2016 and December 31, 2015 , restricted from withdrawal and held by a bank in the form of collateral for an irrevocable standby letter of credit held as security for the lease of the Company's South San Francisco facility signed in April 2015. Supplies Inventory Supplies inventory consists of test reagents and other consumables primarily used in the sample collection kits and in cytopathology and GEC test processing and are valued at the lower of cost or market value. Cost is determined using actual costs on a first-in, first-out basis. Property and Equipment Property and equipment are stated at cost less accumulated depreciation and amortization. Depreciation is computed using the straight-line method over the estimated useful lives of the assets, generally between three and five years . Leasehold improvements are amortized using the straight-line method over the shorter of the estimated useful life of the asset or the term of the lease. Maintenance and repairs are charged to expense as incurred, and improvements and betterments are capitalized. When assets are retired or otherwise disposed of, the cost and accumulated depreciation are removed from the balance sheet and any resulting gain or loss is reflected in the statements of operations and comprehensive loss in the period realized. Business Combination The Company accounts for acquisitions using the acquisition method of accounting which requires the recognition of tangible and identifiable intangible assets acquired and liabilities assumed at their estimated fair values as of the business combination date. The Company allocates any excess purchase price over the estimated fair value assigned to the net tangible and identifiable intangible assets acquired and liabilities assumed to goodwill. Transaction costs are expensed as incurred in general and administrative expenses. Results of operations and cash flows of acquired companies are included in the Company's operating results from the date of acquisition. Finite-lived Intangible Assets Finite-lived intangible assets relate to intangible assets reclassified from indefinite-lived intangible assets, following the launch of Percepta in April 2015. The Company amortizes finite-lived intangible assets using the straight-line method over their estimated useful life. The estimated useful life of 15 years was used for the intangible asset related to the Percepta test based on management's estimate of product life, product life of other diagnostic tests and patent life. The Company tests this finite-lived intangible asset for impairment when events or circumstances indicate a reduction in the fair value below its carrying amount. There was no impairment for either of the years ended December 31, 2016 or 2015 . Goodwill Goodwill, derived from the Company's acquisition of Allegro Diagnostics Corp. (Allegro), is reviewed for impairment on an annual basis or more frequently if events or circumstances indicate that it may be impaired. The Company's goodwill evaluation is based on both qualitative and quantitative assessments regarding the fair value of goodwill relative to its carrying value. The Company has determined that it operates in a single segment and has a single reporting unit associated with the development and commercialization of diagnostic products. In the event the Company determines that it is more likely than not the carrying value of the reporting unit is higher than its fair value, quantitative testing is performed comparing recorded values to estimated fair values. If impairment is present, the impairment loss is measured as the excess of the recorded goodwill over its implied fair value. The Company performs its annual evaluation of goodwill during the fourth quarter of each fiscal year. There was no impairment for the years ended December 31, 2016 , 2015 or 2014 . Fair Value of Financial Instruments The carrying amounts of certain financial instruments including cash and cash equivalents, accounts receivable, prepaid expenses and other current assets, accounts payable and accrued liabilities approximate fair value due to their relatively short maturities. Revenue Recognition The Company recognizes revenue in accordance with the provision of ASC 954-605, Health Care Entities—Revenue Recognition ("ASC 954") . The Company's revenue is generated from the provision of diagnostic services. The service is completed upon the delivery of test results to the prescribing physician, at which time the Company bills for the service. The Company recognizes revenue related to billings for tests delivered on an accrual basis when amounts that will ultimately be realized can be estimated. The estimates of amounts that will ultimately be realized requires significant judgment by management. Until a contract has been negotiated with a commercial payer or governmental program, the Company's tests may or may not be covered by these entities' existing reimbursement policies. In addition, patients do not enter into direct agreements with the Company that commit them to pay any portion of the cost of the tests in the event that their insurance declines to reimburse the Company. The Company may bill the patient directly for these amounts in the form of co-payments and co-insurance in accordance with their insurance carrier and health plans. In the absence of contracted reimbursement or the ability to estimate the amount that will ultimately be realized for the Company's services, revenue is recognized on the cash basis. Revenue recognized for the years ended December 31, 2016 , 2015 and 2014 was as follows (in thousands of dollars): Year Ended December 31, 2016 2015 2014 Revenue recognized on the accrual basis $ 47,099 72 % $ 27,043 55 % $ 12,545 33 % Revenue recognized on the cash basis 17,986 28 % 22,460 45 % 25,645 67 % Total $ 65,085 100 % $ 49,503 100 % $ 38,190 100 % Prior to July 1, 2016, the Company believes it did not have a consistent enough payment history to accrue a significant portion of its Afirma tests delivered to customers and, as noted above, recognized revenue on the cash basis for such tests. The Company has been analyzing the amounts received for tests performed since commercialization and during the quarter ended September 30, 2016, sufficient information developed to support a reasonable estimate of the amount of revenue to accrue upon test delivery for a number of payers that had been previously recognized on the cash basis. In determining the amount to accrue for a particular test, the Company considered factors such as payer coverage, whether there is a reimbursement contract between the payer and the Company, timeliness of payment, payment as a percentage of agreed upon rate (if applicable), amount paid per test and any current developments or changes that could impact reimbursement. As a result, the Company recognized $3.5 million of incremental revenue during the quarter ended September 30, 2016 upon test delivery that previously would not have been recognized until cash was received. Tests performed prior to July 1, 2016 that did not meet the Company’s accrual criteria at the time of delivery will continue to be recognized as revenue on the cash basis. However, the Company expects the amount of revenue to be recognized on the cash basis for Afirma to decline in future periods since subsequent to September 2016 relatively few tests will be performed for which a reasonable estimate of revenue to accrue will not have been made at the time of delivery. The incremental accrued revenue and decrease in loss from operations as a result of additional payers meeting the Company's accrual revenue recognition criteria was $4.1 million , $0.7 million and $0.8 million for tests delivered in the years ended December 31, 2016, 2015 and 2014, respectively. The incremental accrued revenue decreased loss per common share by $0.13 , $0.03 and $0.04 for the years ended December 31, 2016, 2015 and 2014, respectively. Cost of Revenue Cost of revenue is expensed as incurred and includes material and service costs, cytopathology testing services performed by a third-party pathology group, stock-based compensation expense, direct labor costs, equipment and infrastructure expenses associated with testing samples, shipping charges to transport samples, and allocated overhead including rent, information technology, equipment depreciation and utilities. Research and Development Research and development expenses are charged to operations as incurred. Research and development expenses include payroll and personnel-related expenses, stock-based compensation expense, prototype materials, laboratory supplies, consulting costs, costs associated with setting up and conducting clinical studies at domestic and international sites, and allocated overhead including rent, information technology, equipment depreciation and utilities. Income Taxes The Company accounts for income taxes under the liability method. Under this method, deferred tax assets and liabilities are determined based on the difference between the financial statement and tax bases of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to affect taxable income. Valuation allowances are established when necessary to reduce deferred tax assets to the amounts expected to be realized. The Company assesses all material positions taken in any income tax return, including all significant uncertain positions, in all tax years that are still subject to assessment or challenge by relevant taxing authorities. The Company's assessment of an uncertain tax position begins with the initial determination of the position's sustainability and is measured at the largest amount of benefit that is more-likely-than-not of being realized upon ultimate settlement. As of each balance sheet date, unresolved uncertain tax positions must be reassessed, and the Company will determine whether (i) the factors underlying the sustainability assertion have changed and (ii) the amount of the recognized tax benefit is still appropriate. The recognition and measurement of tax benefits requires significant judgment. Judgments concerning the recognition and measurement of a tax benefit may change as new information becomes available. Stock-based Compensation Stock-based compensation expense for equity instruments issued to employees is measured based on the grant-date fair value of the awards. The fair value of each employee stock option is estimated on the date of grant using the Black-Scholes option-pricing model. The Company recognizes compensation costs on a straight-line basis for all employee stock-based compensation awards that are expected to vest over the requisite service period of the awards, which is generally the awards' vesting period. Forfeitures are required to be estimated at the time of grant and revised, if necessary, in subsequent periods if actual forfeitures differ from those estimates. Equity awards issued to non-employees are valued using the Black-Scholes option-pricing model and are subject to re-measurement as the underlying equity awards vest. Net Loss per Common Share Basic net loss per common share is calculated by dividing net loss attributable to common stockholders by the weighted-average number of common shares outstanding during the period, without consideration of common stock equivalents. Diluted net loss per common share is computed by dividing net loss attributable to common stockholders by the weighted-average number of common share equivalents outstanding for the period determined using the treasury stock method. Potentially dilutive securities consisting of options to purchase common stock, restricted stock units and shares subject to purchase under our employee stock purchase plan are considered to be common stock equivalents and were excluded from the calculation of diluted net loss per common share because their effect would be anti-dilutive for all periods presented. Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board ("FASB") issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606), to supersede nearly all existing revenue recognition guidance under GAAP. The core principle of ASU 2014-09 is to recognize revenues when promised goods or services are transferred to customers in an amount that reflects the consideration that is expected to be received for those goods or services. ASU 2014-09 defines a five-step process to achieve this core principle and, in doing so, it is possible more judgment and estimates may be required within the revenue recognition process than are required under existing GAAP, including identifying performance obligations in a contract, estimating the amount of variable consideration to include in the transaction price and allocating the transaction price to each separate performance obligation. The Company will adopt the new revenue standard as of January 1, 2018 using the modified retrospective method. The Company has also completed its assessment of the first step which included identifying the Company’s customers. The Company is currently assessing the remainder of the steps and is in the process of evaluating the effect of adoption of the new revenue standard on its financial statements. In August 2014, FASB issued ASU No. 2014-15, Presentation of Financial Statements Going Concern - Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern . The amendments require management to assess an entity’s ability to continue as a going concern by incorporating and expanding upon certain principles that are currently in U.S. auditing standards. Specifically, the amendments: (1) provide a definition of the term substantial doubt; (2) require an evaluation every reporting period including interim periods; (3) provide principles for considering the mitigating effect of management’s plans; (4) require certain disclosures when substantial doubt is alleviated as a result of consideration of management’s plans; (5) require an express statement and other disclosures when substantial doubt is not alleviated; and (6) require an assessment for a period of one year after the date that the financial statements are issued (or available to be issued). ASU 2014-15 will be effective for annual periods ending after December 15, 2016 and interim periods within annual periods beginning after December 15, 2016 with early adoption permitted. ASU 2014-15 is effective for the Company beginning with its annual report for 2016 and interim periods thereafter. The Company has adopted this ASU and there is no impact on its financial statements. In April 2015, the FASB issued ASU No. 2015-3, Simplifying the Presentation of Debt Issuance Costs , to require debt issuance costs to be presented as an offset against debt outstanding. The update does not change current guidance on the recognition and measurement of debt issuance costs. The ASU is effective for interim and annual periods beginning after December 15, 2015. Adoption of the ASU is retrospective to each prior period presented. The Company has adopted this ASU and the retrospective adjustment of the prior period presentation was not material. In November 2015, the FASB issued ASU 2015-17, Balance Sheet Classification of Deferred Taxes . The ASU requires that deferred tax assets and liabilities be classified as noncurrent in the statement of financial position, thereby simplifying the guidance that required an entity to separate deferred assets and liabilities into current and noncurrent amounts, and was effective for the Company beginning in the first quarter of 2016. The Company early-adopted this ASU as of December 31, 2015 and the impact of adoption on its statement of financial position was not material. In February 2016, the FASB issued ASU No. 2016-2, Leases . This ASU is aimed at making leasing activities more transparent and comparable, and requires substantially all leases be recognized by lessees on their balance sheet as a right-of-use asset and corresponding lease liability, including leases currently accounted for as operating leases. The ASU will be effective for interim and annual periods beginning after December 15, 2018. Early adoption is permitted. The Company is currently evaluating the potential effect of this standard on its financial statements. In March 2016, the FASB issued ASU 2016-9, Compensation - Stock Compensation , related to the tax effects of share-based awards. The ASU requires that all the tax effects of share-based awards be recorded through the income statement, thereby simplifying the current guidance that requires excess tax benefits and certain excess tax deficiencies to be recorded in equity. The ASU is effective for interim and annual periods beginning after December 15, 2016. The Company does not anticipate that the adoption of this ASU will have a significant impact on its financial statements. In November 2016, the FASB issued ASU 2016-18, Statement of Cash Flows - Restricted Cash. This ASU requires that restricted cash and restricted cash equivalents be included with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. The ASU will be effective for interim and annual periods beginning after December 15, 2017. The Company does not anticipate that the adoption of this ASU will have a significant impact on its financial statements.

Net Loss Per Share

Net Loss Per Share	12 Months Ended
	Dec. 31, 2016
Earnings Per Share [Abstract]
Net Loss Per Share	Net Loss Per Share The following outstanding common stock equivalents have been excluded from diluted net loss per common share for the years ended December 31, 2016 , 2015 and 2014 because their inclusion would be anti-dilutive: Year Ended December 31, 2016 2015 2014 Shares of common stock subject to outstanding options 5,093,454 4,086,640 3,035,614 Employee stock purchase plan 36,651 15,561 — Restricted stock units 25,000 — — Total common stock equivalents 5,155,105 4,102,201 3,035,614

Business Combination

Business Combination	12 Months Ended
	Dec. 31, 2016
Business Combinations [Abstract]
Business Combination	Business Combination In September 2014, the Company acquired Allegro via a merger with Full Moon Acquisition, Inc., a wholly-owned subsidiary of the Company focused on the development of genomic tests to improve the preoperative diagnosis of lung cancer. Allegro merged with Full Moon, (the "Merger"), with Allegro surviving the Merger as a wholly-owned subsidiary of the Company. The subsidiary was dissolved in June 2015. At the effective time of the Merger, each share of the common stock of Full Moon issued and outstanding immediately prior to the effective time of the Merger was automatically converted into one share of common stock of Allegro and represented the only outstanding common stock of Allegro at the effective time of the Merger; all previously issued and outstanding shares of common stock of Allegro were canceled. The Series A preferred stock of Allegro issued and outstanding immediately prior to the effective time of the Merger was canceled and automatically converted into the right to receive a total of 964,377 shares of the Company's common stock and $2.7 million in cash. Outstanding indebtedness of Allegro totaling $4.3 million was settled in cash by the Company on the effective date of the Merger. All outstanding stock options under Allegro's equity incentive plan were canceled. The acquisition of Allegro accelerated the Company's entry into the pulmonology diagnostics market. Allegro's lung cancer test is designed to help physicians determine which patients with lung nodules who have had an inconclusive bronchoscopy result are at low risk for cancer and can thus be safely monitored with CT scans rather than undergoing invasive procedures. The Company launched the Percepta test in April 2015. The Merger was accounted for using the acquisition method of accounting with the Company treated as the accounting acquirer. The purchase price was allocated based on the estimated fair value of the assets acquired and liabilities assumed at the date of the acquisition. The Company incurred approximately $0.5 million in acquisition-related costs related to the Merger, which primarily consisted of legal, accounting and valuation-related expenses. In addition, the Company incurred $1.2 million related to transaction bonuses and severance payments to former Allegro employees associated with the Merger. These expenses were recorded in general and administrative expense in the accompanying statements of operations and comprehensive loss. The acquisition consideration was comprised of (in thousands of dollars): Veracyte common stock $ 10,078 Cash 2,725 Payment of outstanding indebtedness 4,290 Total acquisition consideration $ 17,093 The common stock consideration of $10.1 million was determined based on the closing price of the Company's common stock on September 16, 2014 ( $10.45 per share). The fair value of the assets acquired and liabilities assumed at the closing date of the Merger are summarized below (in thousands of dollars): Cash and cash equivalents $ 29 Other assets, net 7 In-process research and development (IPR&D) 16,000 Goodwill 1,057 Total net assets acquired $ 17,093 The fair value of IPR&D was determined using the multi-period excess earnings method of the income approach, which estimates the economic benefits of the IPR&D over multiple time periods by identifying the cash flows associated with the use of the asset, based on forecasts prepared by management, and deducting a periodic charge reflecting a fair return for the use of contributory assets. The forecasted cash flows were discounted based on a discount rate of 18.5% . The discount rate represents the Company's weighted average return on assets and was benchmarked against the internal rate of return and cost of capital of guideline publicly traded companies. The fair value of the IPR&D was capitalized as of the closing date of the Merger and was accounted for as an indefinite-lived intangible asset prior to the beginning of amortization. Amortization of the IPR&D began in April 2015 when research and development activities were deemed to be completed and is recorded on a straight-line basis. The amortization period of the IPR&D is over its estimated useful life of 15 years after taking into consideration expected use of the asset, legal or regulatory provisions that may limit or extend the life of the asset, as well as the effects of obsolescence and other economic factors. Amortization of $1.1 million and $0.8 million was recorded for the years ended December 31, 2016 and 2015 , respectively, and accumulated amortization was $1.9 million and $0.8 million as of December 31, 2016 and 2015 , respectively. Amortization expense will be approximately $1.1 million per year. Goodwill, which represents the purchase price in excess of the fair value of net assets acquired, is not expected to be deductible for income tax purposes. This goodwill is reflective of the value derived from the acceleration of the Company's entry into the pulmonology market. Pro Forma Financial Information (Unaudited) The following pro forma financial information is based on the historical financial statements of the Company and presents the Company's results as if the Merger had occurred as of January 1, 2013 (in thousands of dollars): Year Ended 2014 2013 Revenue $ 38,190 $ 21,884 Net loss $ (29,090 ) $ (28,605 ) The pro forma results present the combined historical results of operations with adjustments to reflect one-time charges including: • The reversal of costs related to transaction bonuses and other payments to employees and acquisition-related expenses directly related to the Merger of $2.2 million for the year ended December 31, 2014 ; and • the elimination of interest expense related to Allegro indebtedness of $2.3 million and $4.5 million for the years ended December 31, 2014 and 2013 , respectively. The pro forma information presented does not purport to present what the actual results would have been had the Merger actually occurred on January 1, 2013, nor is the information intended to project results for any future period.

Balance Sheet Components

Balance Sheet Components	12 Months Ended
	Dec. 31, 2016
Balance Sheet Related Disclosures [Abstract]
Balance Sheet Components	Balance Sheet Components Property and Equipment, Net Property and equipment consisted of the following (in thousands of dollars): Year Ended December 31, 2016 2015 Leasehold improvements $ 5,861 $ 789 Laboratory equipment 6,441 5,501 Computer equipment 1,177 1,046 Software, including software developed for internal use 1,937 1,353 Furniture and fixtures 1,131 242 Construction-in-process 1,769 6,823 Total property and equipment, at cost 18,316 15,754 Accumulated depreciation and amortization (6,836 ) (5,440 ) Total property and equipment, net $ 11,480 $ 10,314 Depreciation and amortization expense was $2.4 million , $1.5 million and $1.2 million for the years ended December 31, 2016 , 2015 and 2014 , respectively. Equipment under a capital lease was purchased in December 2016 but was not available for use at December 31, 2016, and as such, there was no amortization expense for equipment under capital lease in 2016. Accrued Liabilities Accrued liabilities consisted of the following (in thousands of dollars): Year Ended December 31, 2016 2015 Accrued compensation expense $ 6,120 $ 4,212 Accrued Genzyme co-promotion fees — 2,089 Accrued other 2,990 2,388 Total accrued liabilities $ 9,110 $ 8,689

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2016
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements The Company records its financial assets and liabilities at fair value. The carrying amounts of certain financial instruments of the Company, including cash and cash equivalents, prepaid expenses and other current assets, accounts payable and accrued liabilities, approximate fair value due to their relatively short maturities. The carrying value of the Company's debt approximates its fair value because the interest rate approximates market rates that the Company could obtain for debt with similar terms. The estimated fair value of the Company’s debt is estimated using the net present value of the payments, discounted at an interest rate that is consistent with market interest rates, which is a Level II input. The accounting guidance for fair value provides a framework for measuring fair value, clarifies the definition of fair value, and expands disclosures regarding fair value measurements. Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability (an exit price) in an orderly transaction between market participants at the reporting date. The accounting guidance establishes a three-tiered hierarchy, which prioritizes the inputs used in the valuation methodologies in measuring fair value as follows: • Level I: Inputs which include quoted prices in active markets for identical assets and liabilities. • Level II: Inputs other than Level I that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. • Level III: Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. The fair value of the Company's financial assets, which consist only of money market funds, was $58.7 million and $37.5 million as of December 31, 2016 and 2015 respectively, and are Level I assets as described above.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	ommitments and Contingencies Operating Leases The Company leases its headquarters and laboratory facilities in South San Francisco, California under a non-cancelable lease agreement for approximately 59,000 square feet. The lease began in June 2015 and ends in March 2026 and contains extension of lease term and expansion options. Certain expansion options were waived by the Company on February 8, 2017 in exchange for consideration of $500,000 . The Company had deposits of $603,000 included in long-term assets as of December 31, 2016 and 2015 , restricted from withdrawal and held by a bank in the form of collateral for an irrevocable standby letter of credit held as security for the lease of the South San Francisco facility. The Company also leases laboratory and office space in Austin, Texas under a lease that expires on July 31, 2018. The Company provided a cash security deposit of $75,000 , which is included in other assets in the Company's balance sheets as of December 31, 2016 and 2015 . Future minimum lease payments under non-cancelable operating leases as of December 31, 2016 are as follows (in thousands of dollars): Year Ending December 31, Amounts 2017 $ 2,143 2018 2,102 2019 2,026 2020 2,082 2021 2,144 Thereafter 9,812 Total minimum lease payments $ 20,309 The Company recognizes rent expense on a straight-line basis over the non-cancelable lease period. Rent expense was $2.0 million , $1.9 million and $852,000 for the years ended December 31, 2016 , 2015 and 2014 , respectively. Capital Lease The Company entered into a capital lease in December 2016 for $1.2 million of equipment and the associated equipment has not been placed into service as of December 31, 2016 . Amortization of the equipment will commence when the equipment is placed into service and ready for its intended use. The Company paid an upfront amount of $330,000 and the present value of the total future minimum lease payments of $874,000 , which is a non-cash investing transaction for 2016, comprises a short-term portion of $275,000 , included in accrued liabilities, and a long-term portion of $599,000 , included in capital lease liability, on the Company's balance sheet as of December 31, 2016 . As of December 31, 2016 , the annual future minimum lease payments will be $317,000 for each of 2017, 2018 and 2019. Supplies Purchase Commitments The Company had non-cancelable purchase commitments with suppliers to purchase a minimum quantity of supplies for approximately $1.7 million at December 31, 2016 . Contingencies From time to time, the Company may be involved in legal proceedings arising in the ordinary course of business. The Company believes there is no litigation pending that could have, individually or in the aggregate, a material adverse effect on its financial position, results of operations or cash flows.

Debt

Debt	12 Months Ended
	Dec. 31, 2016
Debt Disclosure [Abstract]
Debt	Debt Credit Agreement In March 2016, the Company entered into a credit agreement (the “Credit Agreement”) with Visium Healthcare Partners, LP (“Visium”). Under the Credit Agreement, two term loans are available to the Company with an aggregate principal amount of up to $40.0 million . The Company drew down the initial $25.0 million term loan (the “Initial Term Loan”) on March 30, 2016, of which $5.0 million was used to pay the outstanding balance of the Company’s existing long-term debt, which was cancelled at that date. On or prior to June 30, 2017, the Company may request the second term loan of up to $15.0 million (the “Second Term Loan” and together with the Initial Term Loan, the “Term Loans”). The Term Loans mature on March 31, 2022. The Term Loans bear interest at a fixed rate of 12.0% per annum, payable quarterly at the end of each March, June, September and December. No principal payments will be due during an interest-only period, commencing on the funding date for the Initial Term Loan (the “Initial Borrowing Date”) and continuing through and including March 31, 2020. The Company is obligated to repay the outstanding principal amounts under the Term Loans in eight equal installments during the final two years under the Credit Agreement. For any quarterly interest payment through and including the 16th interest payment date after the Initial Borrowing Date, so long as no event of default has occurred and is then continuing, the Company may elect to pay interest in cash on the outstanding principal amounts of the Term Loans at a fixed rate of 9.0% , with the remaining 3.0% of the 12.0% interest paid-in-kind by adding such paid-in-kind interest to the outstanding principal amounts of the Term Loans. The Company elected to pay interest in-kind for the quarters ended June 30, 2016 and September 30, 2016 and has recorded $385,000 of paid-in-kind interest through December 31, 2016 . The Company may prepay the outstanding principal amount under the Term Loans subject to a minimum of $5.0 million of principal amount or a whole multiple of $1 million in excess thereof plus accrued and unpaid interest and a prepayment premium. The prepayment premium will be assessed on the principal amount repaid and will equal (i) 24.0% less the aggregate amount of all interest payments in cash, if the prepayment is made on or prior to March 31, 2018, (ii) 4.0% , if the prepayment is made after March 31, 2018 and on or prior to March 31, 2019, (iii) 2.0% , if the prepayment is made after March 31, 2019 and on or prior to March 31, 2020, and (iv) 1.0% , if the prepayment is made after March 31, 2020 and on or prior to March 31, 2021. After March 31, 2021 there is no prepayment premium. The Company’s obligations under the Credit Agreement are secured by a security interest in substantially all of its assets. The Credit Agreement contains customary representations, warranties and events of default, as well as affirmative and negative covenants. The negative covenants include, among other provisions, covenants that limit or restrict the Company’s ability to incur liens, make investments, incur indebtedness, merge with or acquire other entities, dispose of assets, make dividends or other distributions to holders of its equity interests, engage in any material new line of business or enter into certain transactions with affiliates, in each case subject to certain exceptions. To the extent the Company forms or acquires certain subsidiaries domiciled in the United States, those subsidiaries are required to be guarantors of the Company’s obligations under the Credit Agreement. As of December 31, 2016 , the Company was in compliance with the loan covenants. Concurrent with entering into the Credit Agreement, the Company entered into an agreement with Visium pursuant to which, for a period of one year following the Initial Borrowing Date, Visium has the right to participate in certain future equity financings of the Company in an amount of up to $5.0 million with no preferential terms. As of December 31, 2016 , the net debt obligation for borrowings made under the Credit Agreement was as follows (in thousands of dollars): December 31, 2016 Debt principal $ 25,385 Unamortized debt issuance costs (467 ) Net debt obligation $ 24,918 Future principal payments under the Credit Agreement are as follows (in thousands of dollars): Year Ending December 31, 2020 $ 9,519 2021 12,693 2022 3,173 Total $ 25,385 Loan and Security Agreement In June 2013, the Company entered into a loan and security agreement ("Original Loan") with a financial institution. The Original Loan provided for term loans of up to $10.0 million in aggregate. The Company drew down $5.0 million in funds under the agreement in June 2013, and did not draw the remaining $5.0 million on or before the expiration date of March 31, 2014. The Company was required to repay the outstanding principal in 30 equal installments beginning 18 months after the date of the borrowing and was due in full in June 2017. The Original Loan had an interest rate of 6.06% per annum, carried prepayment penalties of 2.25% and 1.50% for prepayment within one and two years, respectively, and 0.75% thereafter. In December 2014, the Company amended certain terms and conditions of the Original Loan ("Amended Loan"). The Amended Loan provided for term loans of up to $15.0 million in aggregate, in three tranches of $5.0 million each. The Company borrowed $5.0 million under the first tranche in December 2014 and used the funds for repayment of the $5.0 million in principal outstanding under the Original Loan, in a cashless transaction. In addition, the Company paid the accrued but unpaid interest of $14,000 due on the Original Loan and the related end-of-term payment of $110,000 . The Amended Loan waived the prepayment premium of $75,000 under the Original Loan and reduced the end-of-term payment of $225,000 under the Original Loan to $110,000 . In November 2015, the Company further amended the loan to extend the availability of the second $5.0 million tranche under the Amended Loan through June 30, 2016 from December 31, 2015 originally. The carrying value of the debt approximated its fair value because the interest rate approximated market rates that the Company could have obtained for debt with similar terms. Under the Amended Loan borrowing, the Company was required to repay the outstanding principal in 24 equal installments beginning 24 months after the date of the borrowing and was due in full in December 2018. The first tranche of the Amended Loan bore interest at a rate of 5.00% per annum. The Amended Loan carried prepayment penalties of 2.00% and 1.00% for prepayments within one and two years, respectively, and no prepayment penalty thereafter. In connection with the Amended Loan, the Company paid approximately $45,000 in third-party fees. The Amended Loan resulted in a debt modification under ASC 470-50, Modifications and Extinguishments, as the change in present value of the remaining cash flows associated with the Original Loan and Amended Loan was not substantial. Upon execution of the Original Loan, the Company issued the financial institution a warrant to purchase shares of Series C convertible preferred stock at $7.56 per share. At the time of issuance, the aggregate fair value of the warrant for the 24,801 shares exercisable under the warrant was $175,000 . The fair value of the warrant was deducted from total proceeds, resulting in a debt discount to be amortized to interest expense over 48 months , through the maturity date of the Original Loan, using the effective interest rate method, and was recorded as a preferred stock warrant liability. The warrant was converted to a warrant to purchase the Company's common stock upon the completion of the Company's IPO. The financial institution exercised the warrant with respect to 24,801 shares through a cashless exercise in March 2014, resulting in the issuance of 13,739 shares of the Company's common stock. Borrowings under the 2013 Loan Agreement totaled $5.0 million , which was outstanding at January 1, 2015 and into 2016 until such amount was repaid upon the Company entering into the Credit Agreement discussed above. As of December 31, 2015 , the net debt obligation under the Amended Loan was as follows (in thousands of dollars): 2015 Debt and unpaid accrued end-of-term payment $ 5,082 Unamortized note discount (92 ) Net debt obligation $ 4,990 Interest Expense Interest expense was as follows (in thousands of dollars): Year Ended 2016 2015 2014 Nominal interest $ 2,378 $ 253 $ 296 Amortization and write-off of debt discount and debt issuance costs 173 46 62 End-of-term payment interest and prepayment penalty 206 79 81 Total $ 2,757 $ 378 $ 439

Stockholders' Equity (Deficit)

Stockholders' Equity (Deficit)	12 Months Ended
	Dec. 31, 2016
Equity [Abstract]
Stockholders' Equity (Deficit)	Stockholders' Equity Common Stock The Company's Restated Certificate of Incorporation authorizes the Company to issue 125,000,000 shares of common stock with a par value of $0.001 per share. The holder of each share of common stock shall have one vote for each share of stock. The common stockholders are also entitled to receive dividends whenever funds and assets are legally available and when declared by the Board of Directors, subject to the prior rights of holders of all series of convertible preferred stock outstanding. No dividends have been declared as of December 31, 2016 . As of December 31, 2016 and 2015 , the Company had reserved shares of common stock for issuance as follows: December 31, 2016 2015 Stock options and restricted stock units issued and outstanding 5,251,832 4,179,521 Stock options and restricted stock units available for grant under stock option plans 887,724 1,058,359 Common stock available for the Employee Stock Purchase Plan 609,053 750,000 Total 6,748,609 5,987,880 In November 2016, the Company completed a public offering of 5,723,300 shares of its common stock at a price of $6.00 per share. Gross proceeds to the Company were $34.3 million and the Company raised net proceeds of $32.1 million , after deducting underwriting discounts and commissions and other expenses of $2.2 million . At December 31, 2016, the Company had $200,000 receivable from the underwriters for reimbursement of other expenses, which is included in prepaid expenses and other current assets in the Company's balance sheet. In April 2015, the Company completed a private placement of 4,907,975 shares of its common stock to certain accredited investors at a purchase price of $8.15 per share. Gross proceeds to the Company were $40.0 million and the Company received $37.3 million in net proceeds, after deducting placement agent fees and other expenses of $2.7 million .

Stock Incentive Plans

Stock Incentive Plans	12 Months Ended
	Dec. 31, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock Incentive Plans	Stock Incentive Plans Stock Plans In February 2008, the Company adopted the 2008 Stock Plan (the "2008 Plan"). The 2008 Plan provides for the granting of options to purchase common stock and common stock to employees, directors and consultants of the Company. The Company may grant incentive stock options ("ISOs"), non-statutory stock options ("NSOs") or restricted stock under the 2008 Plan. ISOs may only be granted to Company employees (including directors who are also considered employees). NSOs and restricted stock may be granted to Company employees, directors and consultants. Options may be granted for terms of up to ten years from the date of grant, as determined by the Board of Directors, provided however, that with respect to an ISO granted to a person who owns stock representing more than 10% of the voting power of all classes of stock of the Company, the term shall be for no more than five years from the date of grant. The exercise price of options granted must be at a price no less than 100% of the estimated fair value of the shares on the date of grant, as determined by the Board of Directors, provided however, that with respect to an ISO granted to an employee who at the time of grant of such option owns stock representing more than 10% of the voting power of all classes of stock of the Company, the exercise price shall not be less than 110% of the estimated fair value of the shares on the date of grant. In October 2013, the Company adopted the 2013 Stock Incentive Plan (the "2013 Plan"). The 2013 Plan was subsequently approved by the Company's stockholders and became effective on November 4, 2013, immediately before the closing of the Company's IPO. Following the effectiveness of the 2013 Plan, no additional options will be granted under the 2008 Plan. An aggregate of 1,700,000 shares were initially reserved for issuance under the 2013 Plan. In addition, to the extent that any awards outstanding or subject to vesting restrictions under the 2008 Plan are subsequently forfeited or terminated for any reason before being exercised or settled, the shares of common stock reserved for issuance pursuant to such awards as of the closing of the IPO will become available for issuance under the 2013 Plan. The remaining shares available for grant under the 2008 Plan became available for issuance under the 2013 Plan upon the closing of the IPO. On the first day of each year from 2014 to 2023, the 2013 Plan authorizes an annual increase of the lesser of 4% of outstanding shares on the last day of the immediately preceding fiscal year or a lesser amount as determined by the Company's Board of Directors. As of December 31, 2016, 887,724 shares were available for future issuance under the 2013 Plan. Pursuant to the 2013 Plan, stock options, restricted shares, stock units, including restricted stock units and stock appreciation rights may be granted to employees, consultants, and outside directors of the Company. Options granted may be either ISOs or NSOs. Stock options are governed by stock option agreements between the Company and recipients of stock options. ISOs and NSOs may be granted under the 2013 Plan at an exercise price of not less than 100% of the fair market value of the common stock on the date of grant, determined by the Compensation Committee of the Board of Directors. Options become exercisable and expire as determined by the Compensation Committee, provided that the term of ISOs may not exceed ten years from the date of grant. Stock option agreements may provide for accelerated exercisability in the event of an optionee's death, disability, or retirement or other events. Stock units are governed by stock unit agreements between the Company and recipients of stock units. Stock units may be granted under the 2013 Plan and the number of stock units awarded are determined by the Compensation Committee of the Board of Directors. Stock units vest and expire as determined by the Compensation Committee. Stock unit agreements may provide for accelerated vesting in the event of a stock unit holder's death, disability, or retirement or other events. Any outside director who was not previously an employee and who first joins the Company's Board of Directors on or after the effective date of the 2013 Plan will be automatically granted an initial NSO to purchase 35,000 shares of common stock upon first becoming a member of the Board of Directors. Twenty-five percent of the shares subject to the initial option will vest and become exercisable on the first anniversary of the date of grant. The balance ( i.e., the remaining 75% ) will vest and become exercisable over three years in equal monthly installments. On the first business day after each regularly scheduled annual meeting of stockholders, each outside director who was not elected to the Board of Directors for the first time at such meeting and who will continue serving as a member of the Board of Directors thereafter will be automatically granted an option to purchase 10,000 shares of common stock, provided that the outside director has served on the Board of Directors for at least six months . Each annual option will vest and become exercisable on the first anniversary of the date of grant, or immediately prior to the next regular annual meeting of the Company's stockholders following the date of grant if the meeting occurs prior to the first anniversary date. The options granted to outside directors will have a per share exercise price equal to 100% of the fair market value of the underlying shares on the date of grant and will become fully vested in the event of a change of control. In addition, such options will terminate on the earlier of (i) the day before the 10 th anniversary of the date of grant or (ii) the date 12 months after the termination of the outside director's service for any reason. The following table summarizes activity under the Company's stock incentive plans (aggregate intrinsic value in thousands): Shares Available for Grant Stock Options Weighted Weighted Average Aggregate Balance—December 31, 2015 1,058,359 4,179,521 $ 8.03 7.50 $ 6,511 Additional shares authorized 1,114,416 — Granted - stock options (1,618,250 ) 1,618,250 6.30 Granted - restricted stock units (25,000 ) 25,000 Canceled 358,199 (358,199 ) 10.29 Exercised — (212,740 ) 2.53 Balance—December 31, 2016 887,724 5,251,832 $ 7.56 7.24 $ 8,515 Options vested and exercisable—December 31, 2016 2,628,328 $ 7.42 5.89 $ 6,008 Options vested and expected to vest—December 31, 2016 4,962,370 $ 7.58 7.16 $ 8,254 The aggregate intrinsic value was calculated as the difference between the exercise price of the options to purchase common stock and the fair market value of the Company's common stock, which was $7.74 and $7.20 per share as of December 31, 2016 and 2015, respectively. The weighted average fair value of options to purchase common stock granted was $3.35 , $5.12 and $9.08 for the years ended December 31, 2016, 2015 and 2014, respectively. The aggregate estimated grant date fair value of employee options to purchase common stock vested during the years ended December 31, 2016, 2015 and 2014 was $5.8 million , $5.3 million and $1.6 million , respectively. The intrinsic value of stock options exercised was $0.9 million , $1.8 million and $3.2 million for the years ended December 31, 2016, 2015 and 2014, respectively. The weighted average fair value of restricted stock units granted was $7.47 for the year ended December 31, 2016. Restricted stock units were first issued in December 2016 and there were no restricted stock units vested for the year ended December 31, 2016. Employee Stock Purchase Plan In May 2015, the Company's stockholders approved the Company's Employee Stock Purchase Plan ("ESPP"). The ESPP provides eligible employees with an opportunity to purchase common stock from the Company and to pay for their purchases through payroll deductions. The ESPP will be implemented through a series of offerings of purchase rights to eligible employees. Under the ESPP, the Compensation Committee of the Company's Board of Directors may specify offerings with a duration of not more than 12 months , and may specify shorter purchase periods within each offering. During each purchase period, payroll deductions will accumulate, without interest. On the last day of the purchase period, accumulated payroll deductions will be used to purchase common stock for employees participating in the offering. The purchase price will be specified pursuant to the offering, but cannot, under the terms of the ESPP, be less than 85% of the fair market value per share of the Company's common stock on either the offering date or on the purchase date, whichever is less. The Company's Board of Directors has determined that the purchase periods initially shall have a duration of six months , that the first purchase period began on August 3, 2015 and that the purchase price will be 85% of the fair market value per share of the Company's common stock on either the offering date or the purchase date, whichever is less. The length of the purchase period applicable to U.S. employees and the purchase price may not be changed without the approval of the independent members of the Compensation Committee of the Company's Board of Directors. The Compensation Committee has determined that if the fair market value of a share of the Company's common stock on any purchase date within a particular offering period is less than the fair market value on the start date of that offering period, then the offering period will automatically terminate and the employees in that offering period will automatically be transferred and enrolled in a new offering period which will begin on the next day following such purchase date. No employee is permitted to accrue, under the ESPP, a right to purchase stock of the Company having a value in excess of $25,000 of the fair market value of such stock (determined at the time the right is granted) for each calendar year. Stock-based Compensation The following table summarizes stock-based compensation expense related to stock options, restricted stock units and the ESPP for the years ended December 31, 2016, 2015 and 2014, and are included in the statements of operations and comprehensive loss as follows (in thousands of dollars): Year Ended December 31, 2016 2015 2014 Cost of revenue $ 126 $ 100 $ 51 Research and development 1,322 1,178 790 Selling and marketing 1,594 1,326 707 General and administrative 3,336 2,998 2,000 Total stock-based compensation expense $ 6,378 $ 5,602 $ 3,548 As of December 31, 2016, the Company had $9.3 million of unrecognized compensation expense related to unvested stock options and restricted stock units, which is expected to be recognized over an estimated weighted-average period of 2.50 years . The estimated grant-date fair value of employee stock options was calculated using the Black-Scholes option-pricing model, based on the following assumptions: Year Ended December 31, 2016 2015 2014 Weighted-average volatility 52.49 - 56.36% 52.56 - 68.82% 70.19 - 78.54% Weighted-average expected term (years) 5.50 - 6.27 5.50 - 6.08 5.50 - 6.08 Risk-free interest rate 1.16 - 2.09% 1.55 - 2.03% 1.66 - 2.04% Expected dividend yield — — — The estimated fair value of non-employee stock options was calculated using the Black-Scholes option-pricing model, based on the following assumptions: Year Ended December 31, 2016 2015 2014 Weighted-average volatility 52.77 - 65.85% 64.72 - 74.48% 73.20 - 74.48% Weighted-average expected term (years) 7.80 - 8.56 7.92 - 10.00 8.75 - 10.00 Risk-free interest rate 1.39 - 2.30% 1.78 - 2.29% 2.09 - 2.20% Expected dividend yield — — — The estimated grant date fair value of the ESPP shares was calculated using the Black-Scholes option-pricing model, based on the following assumptions: Year Ended December 31, 2016 2015 Weighted-average volatility 46.38 - 75.72% 53.57 - 58.10% Weighted-average expected term (years) 0.50 - 1.00 0.49 - 0.99 Risk-free interest rate 0.40 - 0.50% 0.17 - 0.33% Expected dividend yield — —

Genzyme Co-promotion Agreement

Genzyme Co-promotion Agreement	12 Months Ended
	Dec. 31, 2016
Genzyme Co-promotion Agreement
Genzyme Co-promotion Agreement	Genzyme Co-Promotion Agreement In January 2012, the Company and Genzyme Corporation ("Genzyme") executed a co-promotion agreement for the co-exclusive rights and license to promote and market the Company's Afirma thyroid diagnostic solution in the United States and in 40 named countries. In exchange, the Company received a $10.0 million upfront co-promotion fee from Genzyme in February 2012. Under the terms of the agreement, Genzyme received a percentage of U.S. cash receipts that the Company has received related to Afirma as co-promotion fees. The percentage was 50% in 2012, 40% from January 2013 through February 2014, and 32% beginning in February 2014. In November 2014, the Company signed an Amended and Restated U.S. Co-Promotion Agreement ("Amended Agreement") with Genzyme. Under the Amended Agreement, the co-promotion fees Genzyme receives as a percentage of U.S. cash receipts were reduced from 32% to 15% beginning January 1, 2015. Through August 11, 2014, the Company amortized the $10.0 million upfront co-promotion fee on a straight-line basis over a four -year period, which was management's estimate of the life of the agreement, in part because after that period either party could have terminated the agreement without penalty. Effective August 12, 2014, the Company extended the amortization period from January 2016 to June 2016, the modified earliest period either party could terminate the agreement without penalty. The Company accounted for the change in accounting estimate prospectively. The agreement was terminable by either party with six months prior notice, however, under the Amended Agreement, neither party could terminate the agreement for convenience prior to June 30, 2016. The agreement with Genzyme was to expire in 2027. On March 9, 2016, the Company gave Genzyme notice of termination of the Amended Agreement effective September 9, 2016 and the amortization of the upfront co-promotion fee was further extended to that date. The extension of the amortization period had no impact on the Company's 2016 financial statements on an annual basis. In February 2015, the Company entered into an Ex-U.S. Co-promotion Agreement with Genzyme for the promotion of the Afirma GEC test with exclusivity in five countries outside the United States initially and in other countries agreed to from time to time. The agreement commenced on January 1, 2015 and continues until December 31, 2019, with extension of the agreement possible upon agreement of the parties. Country-specific terms have been established under this agreement for Brazil and Singapore and a right of first negotiation has been established for Canada, the Netherlands and Italy. The Company pays Genzyme 25% of net revenue from the sale of the Afirma GEC test in Brazil and Singapore over a five -year period commencing January 1, 2015. These payments have been immaterial for all periods presented. Beginning in the fourth year of the agreement, if the Company terminates the agreement for convenience, the Company may be required to pay a termination fee contingent on the number of GEC billable results generated during the 12 months immediately prior to the notice of termination. The Company incurred $6.1 million , $7.3 million and $12.0 million in co-promotion expense, excluding the amortization of the upfront co-promotion fee, in the years ended December 31, 2016, 2015 and 2014, respectively, which is included in selling and marketing expenses in the statements of operations and comprehensive loss. The Company had no obligation to Genzyme at December 31, 2016 compared to $2.1 million at December 31, 2015, which is included in accrued liabilities on the Company's balance sheets. The Company amortized $0.9 million , $1.9 million and $2.3 million of the $10.0 million upfront co-promotion fee in the years ended December 31, 2016, 2015 and 2014, respectively, which is reflected as a reduction to selling and marketing expenses in the statements of operations and comprehensive loss.

Thyroid Cytopathology Partners

Thyroid Cytopathology Partners	12 Months Ended
	Dec. 31, 2016
Thyroid Cytopathology Partners
Thyroid Cytopathology Partners	Thyroid Cytopathology Partners In 2010, the Company entered into an arrangement with Pathology Resource Consultants, P.A. ("PRC") to set up and manage a specialized pathology practice to provide testing services to the Company. There is no direct monetary compensation from the Company to PRC as a result of this arrangement. The Company's service agreement is with the specialized pathology practice, Thyroid Cytopathology Partners, ("TCP"), and was effective through December 31, 2015, and thereafter automatically renews every year unless either party provides notice of intent not to renew at least 12 months prior to the end of the then-current term. Under the service agreement, the Company pays TCP based on a fixed price per test schedule, which is reviewed periodically for changes in market pricing. Subsequent to December 2012, an amendment to the service agreement allows TCP to sublease a portion of the Company's facility in Austin, Texas. The Company does not have an ownership interest in or provide any form of financial or other support to TCP. The Company has concluded that TCP represents a variable interest entity and that the Company is not the primary beneficiary as it does not have the ability to direct the activities that most significantly impact TCP's economic performance. Therefore, the Company does not consolidate TCP. All amounts paid to TCP under the service agreement are expensed as incurred and included in cost of revenue in the statements of operations and comprehensive loss. The Company incurred $5.1 million , $4.7 million and $4.0 million for the years ended December 31, 2016 , 2015 and 2014 , respectively, in cytopathology testing and evaluation services expenses with TCP. The Company's outstanding obligations to TCP for cytopathology testing services were $426,000 and $820,000 as of December 31, 2016 and 2015 , respectively, and are included in accounts payable in the Company's balance sheets. TCP reimburses the Company for TCP's proportionate share of the Company's rent and related operating expenses for the leased facility. TCP's portion of rent and related operating expenses for the shared space at the Austin, Texas facility was $103,000 , $90,000 and $86,000 for the years ended December 31, 2016 , 2015 and 2014 and is included other income, net in the Company's statements of operations and comprehensive loss.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The Company generated a pretax loss of $31.4 million , $33.7 million and $29.4 million in the United States for the years ended December 31, 2016 , 2015 and 2014 , respectively. Since inception, the Company has not generated any pretax income or loss outside of the United States. The Company recorded no provision for income taxes during the years ended December 31, 2016 , 2015 or 2014 . The Company follows FASB ASC No. 740, Income Taxes for the Computation and Presentation of its Tax Provision. The following table presents a reconciliation of the tax expense computed at the statutory federal rate and the Company's tax expense for the periods presented (in thousands of dollars): Year Ended December, 31, 2016 2015 2014 U.S. federal taxes at statutory rate $ (10,662 ) $ (11,459 ) $ (9,987 ) State tax (net of federal benefit) 20 (30 ) 5 Permanent differences 153 96 64 Incentive stock options 1,095 789 672 Tax credits (677 ) (581 ) (461 ) Change in valuation allowance 10,071 11,185 9,707 Total $ — $ — $ — Deferred income taxes reflect the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. Significant components of the Company's deferred tax assets and liabilities are as follows (in thousands of dollars): Year Ended December 31, 2016 2015 2014 Deferred tax assets: Net operating loss carryforwards $ 61,674 $ 52,262 $ 41,971 Research and development credits 3,174 2,497 1,916 Stock-based compensation 2,847 1,825 826 Genzyme co-promotion agreement — 330 995 Accruals, deferred rent and other 4,511 4,698 3,381 Gross deferred tax assets 72,206 61,612 49,089 Valuation allowance (65,975 ) (55,101 ) (43,439 ) Net deferred tax assets 6,231 6,511 5,650 Deferred tax liabilities: Property and equipment (1,180 ) (1,215 ) (60 ) In-process research and development (5,051 ) (5,296 ) (5,590 ) Gross deferred tax liabilities (6,231 ) (6,511 ) (5,650 ) Net deferred tax liabilities (6,231 ) (6,511 ) (5,650 ) Net deferred taxes $ — $ — $ — In November 2015, the FASB issued ASU 2015-17, Balance Sheet Classification of Deferred Taxes , related to balance sheet classification of deferred taxes. The ASU requires that deferred tax assets and liabilities be classified as noncurrent in the statement of financial position, thereby simplifying the guidance that required an entity to separate deferred assets and liabilities into current and noncurrent amounts, and was effective for the Company beginning in the first quarter of 2016. The Company early-adopted the ASU as of December 31, 2015 and its statement of financial position as of this date reflects the revised classification of current deferred tax assets and liabilities as noncurrent. The Company has established a full valuation allowance against its net deferred tax assets due to the uncertainty surrounding realization of such assets. The valuation allowance increased $10.9 million , $11.7 million and $10.6 million during the years ended December 31, 2016 , 2015 and 2014 , respectively. As of December 31, 2016 , the Company had net operating loss carryforwards of approximately $169.1 million and $84.2 million available to reduce future taxable income, if any, for federal and state income tax purposes, respectively. Of these amounts, $1.6 million represent federal and state excess tax deductions from stock-based compensation, which will be recorded as an adjustment to additional paid-in capital when they reduce tax payable. The U.S. federal net operating loss carryforwards will begin to expire in 2026 while for state purposes, the net operating losses began to expire in 2016. As of December 31, 2016 , the Company had net credit carryforwards of approximately $3.3 million and $2.7 million available to reduce future taxable income, if any, for federal and state income tax purposes, respectively. The federal credit carryforwards begin to expire in 2028 . California credits have no expiration date. Other state credit carryforwards begin to expire in 2023 . On December 18, 2015, The Consolidated Appropriations Act of 2014 was signed into law, which retroactively reinstated and made permanent the federal research tax credit provisions from January 1, 2015 through December 31, 2015. The Internal Revenue Code of 1986, as amended, imposes restrictions on the utilization of net operating losses and tax credits in the event of an "ownership change" of a corporation. Accordingly, a company's ability to use net operating losses and tax credits may be limited as prescribed under Internal Revenue Code Section 382 and 383 ("IRC Section 382"). Events which may cause limitations in the amount of the net operating losses or tax credits that the Company may use in any one year include, but are not limited to, a cumulative ownership change of more than 50% over a three-year period. Utilization of the federal and state net operating losses may be subject to substantial annual limitation due to the ownership change limitations provided by the IRC Section 382 rules and similar state provisions. In the event the Company has any changes in ownership, net operating losses and research and development credit carryovers could be limited and may expire unutilized. Uncertain Tax Positions As of December 31, 2016 , the Company had unrecognized tax benefits of $2.2 million , none of which would currently affect the Company's effective tax rate if recognized due to the Company's deferred tax assets being fully offset by a valuation allowance. The Company does not anticipate that the amount of unrecognized tax benefits relating to tax positions existing at December 31, 2016 will significantly increase or decrease within the next 12 months. A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows (in thousands of dollars): Year Ended December 31, 2016 2015 2014 Unrecognized tax benefits, beginning of period $ 1,871 $ 1,571 $ 727 Gross increases—tax position in prior period — — 548 Gross decreases—tax position in prior period — — — Gross increases—current period tax position 351 300 296 Lapse of statute of limitations — — — Unrecognized tax benefits, end of period $ 2,222 $ 1,871 $ 1,571 It is the Company's policy to include penalties and interest expense related to income taxes as a component of other income (expense), net, and interest expense, respectively, as necessary. There was no interest expense or penalties related to unrecognized tax benefits recorded through December 31, 2016 . The Company's major tax jurisdictions are the United States and California. All of the Company's tax years will remain open for examination by the Federal and state tax authorities for three and four years , respectively, from the date of utilization of the net operating loss or research and development credit. The Company does not have any tax audits pending.

401(k) Plan

401(k) Plan	12 Months Ended
	Dec. 31, 2016
Compensation and Retirement Disclosure [Abstract]
401(k) Plan	401(k) Plan The Company sponsors a 401(k) defined contribution plan covering all employees. Employer contributions to the plan were $262,000 and $103,000 for the years ended December 31, 2016 and 2015 , respectively. There were no employer contributions to the plan for the year ended December 31, 2014 .

Selected Quarterly Financial Da

Selected Quarterly Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Selected Quarterly Financial Data (Unaudited)	Selected Quarterly Financial Data (Unaudited) The following table presents selected unaudited financial data for each of the eight quarters in the two-year period ended December 31, 2016 . The Company believes this information reflects all recurring adjustments necessary to fairly present this information when read in conjunction with the Company's financial statements and the related notes. Net loss per common share, basic and diluted, for the four quarters of each fiscal year may not sum to the total for the fiscal year because of the different number of shares outstanding during each period. The results of operations for any quarter are not necessarily indicative of the results to be expected for any future period (in thousands of dollars, except for share and per share data): Quarter Ended March 31 June 30 September 30 December 31 2016: Revenue $ 13,550 $ 14,675 $ 18,603 $ 18,257 Net loss (10,075 ) (11,243 ) (5,637 ) (4,403 ) Net loss per common share, basic and diluted (0.36 ) (0.40 ) (0.20 ) (0.14 ) Shares used to compute net loss per common share, basic and diluted 27,817,993 27,859,918 27,916,819 31,705,603 2015: Revenue $ 11,218 $ 11,908 $ 12,335 $ 14,042 Net loss (7,610 ) (9,136 ) (8,945 ) (8,013 ) Net loss per common share, basic and diluted (0.34 ) (0.35 ) (0.32 ) (0.29 ) Shares used to compute net loss per common share, basic and diluted 22,539,723 26,048,934 27,640,806 27,672,806

Summary of Significant Accoun22

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2016
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The Company's financial statements have been prepared in accordance with accounting principles generally accepted in the United States ("GAAP"). The financial statements include the accounts of the Company and its former wholly-owned subsidiary, which was dissolved in June 2015. For periods prior to the subsidiary dissolution, all intercompany accounts and transactions were eliminated in consolidation. Certain amounts have been reclassified on the balance sheet at December 31, 2015 to conform with the adoption of Accounting Standards Update (“ASU”) No. 2015-3, Simplifying the Presentation of Debt Issuance Costs.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities as of the date of the financial statements and the reported amounts of revenue and expenses during the reporting period. Significant items subject to such estimates include: revenue recognition; contractual allowances; the useful lives of property and equipment; the recoverability of long-lived assets; the estimation of the fair value of intangible assets; stock options; income tax uncertainties, including a valuation allowance for deferred tax assets; and contingencies. The Company bases these estimates on historical and anticipated results, trends, and various other assumptions that the Company believes are reasonable under the circumstances, including assumptions as to future events. These estimates form the basis for making judgments about the carrying values of assets and liabilities and recorded revenue and expenses that are not readily apparent from other sources. Actual results could differ from those estimates and assumptions.
Concentrations of Credit Risk and Other Risks and Uncertainties	Concentrations of Credit Risk and Other Risks and Uncertainties The majority of the Company's cash and cash equivalents are deposited with one major financial institution in the United States. Deposits in this institution may exceed the amount of insurance provided on such deposits. The Company has not experienced any losses on its deposits of cash and cash equivalents. Several of the components of the Company's sample collection kit and test reagents are obtained from single-source suppliers. If these single-source suppliers fail to satisfy the Company's requirements on a timely basis, it could suffer delays in being able to deliver its diagnostic solutions, a possible loss of revenue, or incur higher costs, any of which could adversely affect its operating results. The Company is also subject to credit risk from its accounts receivable related to its sales. The Company generally does not perform evaluations of customers' financial condition and generally does not require collateral.
Cash Equivalents	Cash Equivalents Cash equivalents consist of short-term, highly liquid investments with original maturities of three months or less from the date of purchase. Cash equivalents consist of amounts invested in a money market account primarily consisting of U.S. Treasury reserves.
Restricted Cash	Restricted Cash The Company had deposits of $120,000 and $118,000 as of December 31, 2016 and December 31, 2015 , respectively, included in current assets. The deposit at December 31, 2016 was a pledge for corporate credit cards and the deposit at December 31, 2015 was restricted from withdrawal and held by a bank in the form of collateral for irrevocable standby letters of credit held as security for the lease of the Company's former headquarters and laboratory facilities in South San Francisco that expired March 31, 2016. The Company also had deposits of $603,000 included in long-term assets as of December 31, 2016 and December 31, 2015 , restricted from withdrawal and held by a bank in the form of collateral for an irrevocable standby letter of credit held as security for the lease of the Company's South San Francisco facility signed in April 2015.
Supplies Inventory	Supplies Inventory Supplies inventory consists of test reagents and other consumables primarily used in the sample collection kits and in cytopathology and GEC test processing and are valued at the lower of cost or market value. Cost is determined using actual costs on a first-in, first-out basis.
Property and Equipment	Property and Equipment Property and equipment are stated at cost less accumulated depreciation and amortization. Depreciation is computed using the straight-line method over the estimated useful lives of the assets, generally between three and five years . Leasehold improvements are amortized using the straight-line method over the shorter of the estimated useful life of the asset or the term of the lease. Maintenance and repairs are charged to expense as incurred, and improvements and betterments are capitalized. When assets are retired or otherwise disposed of, the cost and accumulated depreciation are removed from the balance sheet and any resulting gain or loss is reflected in the statements of operations and comprehensive loss in the period realized.
Business Combination	Business Combination The Company accounts for acquisitions using the acquisition method of accounting which requires the recognition of tangible and identifiable intangible assets acquired and liabilities assumed at their estimated fair values as of the business combination date. The Company allocates any excess purchase price over the estimated fair value assigned to the net tangible and identifiable intangible assets acquired and liabilities assumed to goodwill. Transaction costs are expensed as incurred in general and administrative expenses. Results of operations and cash flows of acquired companies are included in the Company's operating results from the date of acquisition.
Finite-lived Intangible Assets	Finite-lived Intangible Assets Finite-lived intangible assets relate to intangible assets reclassified from indefinite-lived intangible assets, following the launch of Percepta in April 2015. The Company amortizes finite-lived intangible assets using the straight-line method over their estimated useful life. The estimated useful life of 15 years was used for the intangible asset related to the Percepta test based on management's estimate of product life, product life of other diagnostic tests and patent life. The Company tests this finite-lived intangible asset for impairment when events or circumstances indicate a reduction in the fair value below its carrying amount. There was no impairment for either of the years ended December 31, 2016 or 2015 .
Goodwill	Goodwill Goodwill, derived from the Company's acquisition of Allegro Diagnostics Corp. (Allegro), is reviewed for impairment on an annual basis or more frequently if events or circumstances indicate that it may be impaired. The Company's goodwill evaluation is based on both qualitative and quantitative assessments regarding the fair value of goodwill relative to its carrying value. The Company has determined that it operates in a single segment and has a single reporting unit associated with the development and commercialization of diagnostic products. In the event the Company determines that it is more likely than not the carrying value of the reporting unit is higher than its fair value, quantitative testing is performed comparing recorded values to estimated fair values. If impairment is present, the impairment loss is measured as the excess of the recorded goodwill over its implied fair value. The Company performs its annual evaluation of goodwill during the fourth quarter of each fiscal year. There was no impairment for the years ended December 31, 2016 , 2015 or 2014 .
Fair Value of Financial Instruments	Fair Value of Financial Instruments The carrying amounts of certain financial instruments including cash and cash equivalents, accounts receivable, prepaid expenses and other current assets, accounts payable and accrued liabilities approximate fair value due to their relatively short maturities.
Revenue Recognition	Revenue Recognition The Company recognizes revenue in accordance with the provision of ASC 954-605, Health Care Entities—Revenue Recognition ("ASC 954") . The Company's revenue is generated from the provision of diagnostic services. The service is completed upon the delivery of test results to the prescribing physician, at which time the Company bills for the service. The Company recognizes revenue related to billings for tests delivered on an accrual basis when amounts that will ultimately be realized can be estimated. The estimates of amounts that will ultimately be realized requires significant judgment by management. Until a contract has been negotiated with a commercial payer or governmental program, the Company's tests may or may not be covered by these entities' existing reimbursement policies. In addition, patients do not enter into direct agreements with the Company that commit them to pay any portion of the cost of the tests in the event that their insurance declines to reimburse the Company. The Company may bill the patient directly for these amounts in the form of co-payments and co-insurance in accordance with their insurance carrier and health plans. In the absence of contracted reimbursement or the ability to estimate the amount that will ultimately be realized for the Company's services, revenue is recognized on the cash basis.
Cost of Revenue	Cost of Revenue Cost of revenue is expensed as incurred and includes material and service costs, cytopathology testing services performed by a third-party pathology group, stock-based compensation expense, direct labor costs, equipment and infrastructure expenses associated with testing samples, shipping charges to transport samples, and allocated overhead including rent, information technology, equipment depreciation and utilities.
Research and Development	Research and Development Research and development expenses are charged to operations as incurred. Research and development expenses include payroll and personnel-related expenses, stock-based compensation expense, prototype materials, laboratory supplies, consulting costs, costs associated with setting up and conducting clinical studies at domestic and international sites, and allocated overhead including rent, information technology, equipment depreciation and utilities.
Income Taxes	Income Taxes The Company accounts for income taxes under the liability method. Under this method, deferred tax assets and liabilities are determined based on the difference between the financial statement and tax bases of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to affect taxable income. Valuation allowances are established when necessary to reduce deferred tax assets to the amounts expected to be realized. The Company assesses all material positions taken in any income tax return, including all significant uncertain positions, in all tax years that are still subject to assessment or challenge by relevant taxing authorities. The Company's assessment of an uncertain tax position begins with the initial determination of the position's sustainability and is measured at the largest amount of benefit that is more-likely-than-not of being realized upon ultimate settlement. As of each balance sheet date, unresolved uncertain tax positions must be reassessed, and the Company will determine whether (i) the factors underlying the sustainability assertion have changed and (ii) the amount of the recognized tax benefit is still appropriate. The recognition and measurement of tax benefits requires significant judgment. Judgments concerning the recognition and measurement of a tax benefit may change as new information becomes available.
Stock-based Compensation	Stock-based Compensation Stock-based compensation expense for equity instruments issued to employees is measured based on the grant-date fair value of the awards. The fair value of each employee stock option is estimated on the date of grant using the Black-Scholes option-pricing model. The Company recognizes compensation costs on a straight-line basis for all employee stock-based compensation awards that are expected to vest over the requisite service period of the awards, which is generally the awards' vesting period. Forfeitures are required to be estimated at the time of grant and revised, if necessary, in subsequent periods if actual forfeitures differ from those estimates. Equity awards issued to non-employees are valued using the Black-Scholes option-pricing model and are subject to re-measurement as the underlying equity awards vest.
Net Loss per Common Share	Net Loss per Common Share Basic net loss per common share is calculated by dividing net loss attributable to common stockholders by the weighted-average number of common shares outstanding during the period, without consideration of common stock equivalents. Diluted net loss per common share is computed by dividing net loss attributable to common stockholders by the weighted-average number of common share equivalents outstanding for the period determined using the treasury stock method. Potentially dilutive securities consisting of options to purchase common stock, restricted stock units and shares subject to purchase under our employee stock purchase plan are considered to be common stock equivalents and were excluded from the calculation of diluted net loss per common share because their effect would be anti-dilutive for all periods presented.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board ("FASB") issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606), to supersede nearly all existing revenue recognition guidance under GAAP. The core principle of ASU 2014-09 is to recognize revenues when promised goods or services are transferred to customers in an amount that reflects the consideration that is expected to be received for those goods or services. ASU 2014-09 defines a five-step process to achieve this core principle and, in doing so, it is possible more judgment and estimates may be required within the revenue recognition process than are required under existing GAAP, including identifying performance obligations in a contract, estimating the amount of variable consideration to include in the transaction price and allocating the transaction price to each separate performance obligation. The Company will adopt the new revenue standard as of January 1, 2018 using the modified retrospective method. The Company has also completed its assessment of the first step which included identifying the Company’s customers. The Company is currently assessing the remainder of the steps and is in the process of evaluating the effect of adoption of the new revenue standard on its financial statements. In August 2014, FASB issued ASU No. 2014-15, Presentation of Financial Statements Going Concern - Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern . The amendments require management to assess an entity’s ability to continue as a going concern by incorporating and expanding upon certain principles that are currently in U.S. auditing standards. Specifically, the amendments: (1) provide a definition of the term substantial doubt; (2) require an evaluation every reporting period including interim periods; (3) provide principles for considering the mitigating effect of management’s plans; (4) require certain disclosures when substantial doubt is alleviated as a result of consideration of management’s plans; (5) require an express statement and other disclosures when substantial doubt is not alleviated; and (6) require an assessment for a period of one year after the date that the financial statements are issued (or available to be issued). ASU 2014-15 will be effective for annual periods ending after December 15, 2016 and interim periods within annual periods beginning after December 15, 2016 with early adoption permitted. ASU 2014-15 is effective for the Company beginning with its annual report for 2016 and interim periods thereafter. The Company has adopted this ASU and there is no impact on its financial statements. In April 2015, the FASB issued ASU No. 2015-3, Simplifying the Presentation of Debt Issuance Costs , to require debt issuance costs to be presented as an offset against debt outstanding. The update does not change current guidance on the recognition and measurement of debt issuance costs. The ASU is effective for interim and annual periods beginning after December 15, 2015. Adoption of the ASU is retrospective to each prior period presented. The Company has adopted this ASU and the retrospective adjustment of the prior period presentation was not material. In November 2015, the FASB issued ASU 2015-17, Balance Sheet Classification of Deferred Taxes . The ASU requires that deferred tax assets and liabilities be classified as noncurrent in the statement of financial position, thereby simplifying the guidance that required an entity to separate deferred assets and liabilities into current and noncurrent amounts, and was effective for the Company beginning in the first quarter of 2016. The Company early-adopted this ASU as of December 31, 2015 and the impact of adoption on its statement of financial position was not material. In February 2016, the FASB issued ASU No. 2016-2, Leases . This ASU is aimed at making leasing activities more transparent and comparable, and requires substantially all leases be recognized by lessees on their balance sheet as a right-of-use asset and corresponding lease liability, including leases currently accounted for as operating leases. The ASU will be effective for interim and annual periods beginning after December 15, 2018. Early adoption is permitted. The Company is currently evaluating the potential effect of this standard on its financial statements. In March 2016, the FASB issued ASU 2016-9, Compensation - Stock Compensation , related to the tax effects of share-based awards. The ASU requires that all the tax effects of share-based awards be recorded through the income statement, thereby simplifying the current guidance that requires excess tax benefits and certain excess tax deficiencies to be recorded in equity. The ASU is effective for interim and annual periods beginning after December 15, 2016. The Company does not anticipate that the adoption of this ASU will have a significant impact on its financial statements. In November 2016, the FASB issued ASU 2016-18, Statement of Cash Flows - Restricted Cash. This ASU requires that restricted cash and restricted cash equivalents be included with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. The ASU will be effective for interim and annual periods beginning after December 15, 2017. The Company does not anticipate that the adoption of this ASU will have a significant impact on its financial statements.

Summary of Significant Accoun23

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2016
Revenue Recognition
Schedule of Revenue recognized when cash is received and on an accrual basis	Revenue recognized for the years ended December 31, 2016 , 2015 and 2014 was as follows (in thousands of dollars): Year Ended December 31, 2016 2015 2014 Revenue recognized on the accrual basis $ 47,099 72 % $ 27,043 55 % $ 12,545 33 % Revenue recognized on the cash basis 17,986 28 % 22,460 45 % 25,645 67 % Total $ 65,085 100 % $ 49,503 100 % $ 38,190 100 %
Revenue concentration risk | Revenue
Concentration Risk
Schedule of the Company's third-party payers as a percentage of total	The Company's third-party payers in excess of 10% of revenue and their related revenue as a percentage of total revenue were as follows: Year Ended December 31, 2016 2015 2014 Medicare 27 % 26 % 26 % UnitedHealthcare 12 % 14 % 18 % Aetna 8 % 9 % 11 % 47 % 49 % 55 %
Gross receivables concentration risk | Accounts receivable
Concentration Risk
Schedule of the Company's third-party payers as a percentage of total	The Company's significant third-party payers and their related accounts receivable balance as a percentage of total accounts receivable were as follows: December 31, 2016 2015 Medicare 18 % 31 % UnitedHealthcare 8 % 25 % Aetna 4 % 23 %

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	12 Months Ended
	Dec. 31, 2016
Earnings Per Share [Abstract]
Schedule of outstanding shares of common stock equivalents that have been excluded from diluted net loss per common share	The following outstanding common stock equivalents have been excluded from diluted net loss per common share for the years ended December 31, 2016 , 2015 and 2014 because their inclusion would be anti-dilutive: Year Ended December 31, 2016 2015 2014 Shares of common stock subject to outstanding options 5,093,454 4,086,640 3,035,614 Employee stock purchase plan 36,651 15,561 — Restricted stock units 25,000 — — Total common stock equivalents 5,155,105 4,102,201 3,035,614

Business Combination (Tables)

Business Combination (Tables)	12 Months Ended
	Dec. 31, 2016
Business Combination
Schedule of pro forma financial information as if the Merger had occurred as of January 1, 2013	The following pro forma financial information is based on the historical financial statements of the Company and presents the Company's results as if the Merger had occurred as of January 1, 2013 (in thousands of dollars): Year Ended 2014 2013 Revenue $ 38,190 $ 21,884 Net loss $ (29,090 ) $ (28,605 )
Allegro
Business Combination
Schedule of acquisition consideration	The acquisition consideration was comprised of (in thousands of dollars): Veracyte common stock $ 10,078 Cash 2,725 Payment of outstanding indebtedness 4,290 Total acquisition consideration $ 17,093
Schedule of fair value of assets acquired and liabilities assumed	The fair value of the assets acquired and liabilities assumed at the closing date of the Merger are summarized below (in thousands of dollars): Cash and cash equivalents $ 29 Other assets, net 7 In-process research and development (IPR&D) 16,000 Goodwill 1,057 Total net assets acquired $ 17,093

Balance Sheet Components (Table

Balance Sheet Components (Tables)	12 Months Ended
	Dec. 31, 2016
Balance Sheet Related Disclosures [Abstract]
Schedule of property and equipment	Property and equipment consisted of the following (in thousands of dollars): Year Ended December 31, 2016 2015 Leasehold improvements $ 5,861 $ 789 Laboratory equipment 6,441 5,501 Computer equipment 1,177 1,046 Software, including software developed for internal use 1,937 1,353 Furniture and fixtures 1,131 242 Construction-in-process 1,769 6,823 Total property and equipment, at cost 18,316 15,754 Accumulated depreciation and amortization (6,836 ) (5,440 ) Total property and equipment, net $ 11,480 $ 10,314
Schedule of accrued liabilities	Accrued liabilities consisted of the following (in thousands of dollars): Year Ended December 31, 2016 2015 Accrued compensation expense $ 6,120 $ 4,212 Accrued Genzyme co-promotion fees — 2,089 Accrued other 2,990 2,388 Total accrued liabilities $ 9,110 $ 8,689

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Schedule of future minimum lease payments under non-cancelable operating leases	Future minimum lease payments under non-cancelable operating leases as of December 31, 2016 are as follows (in thousands of dollars): Year Ending December 31, Amounts 2017 $ 2,143 2018 2,102 2019 2,026 2020 2,082 2021 2,144 Thereafter 9,812 Total minimum lease payments $ 20,309

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2016
Debt Instrument [Line Items]
Schedule of interest expense on debt	Interest expense was as follows (in thousands of dollars): Year Ended 2016 2015 2014 Nominal interest $ 2,378 $ 253 $ 296 Amortization and write-off of debt discount and debt issuance costs 173 46 62 End-of-term payment interest and prepayment penalty 206 79 81 Total $ 2,757 $ 378 $ 439
Line of Credit
Debt Instrument [Line Items]
Schedule of future principal payments under the Amended Loan	Future principal payments under the Credit Agreement are as follows (in thousands of dollars): Year Ending December 31, 2020 $ 9,519 2021 12,693 2022 3,173 Total $ 25,385
Schedule of net debt obligation	As of December 31, 2016 , the net debt obligation for borrowings made under the Credit Agreement was as follows (in thousands of dollars): December 31, 2016 Debt principal $ 25,385 Unamortized debt issuance costs (467 ) Net debt obligation $ 24,918
Term Loan
Debt Instrument [Line Items]
Schedule of net debt obligation	As of December 31, 2015 , the net debt obligation under the Amended Loan was as follows (in thousands of dollars): 2015 Debt and unpaid accrued end-of-term payment $ 5,082 Unamortized note discount (92 ) Net debt obligation $ 4,990

Stockholders' Equity (Deficit)

Stockholders' Equity (Deficit) (Tables)	12 Months Ended
	Dec. 31, 2016
Equity [Abstract]
Schedule of reserved shares of common stock for issuance	As of December 31, 2016 and 2015 , the Company had reserved shares of common stock for issuance as follows: December 31, 2016 2015 Stock options and restricted stock units issued and outstanding 5,251,832 4,179,521 Stock options and restricted stock units available for grant under stock option plans 887,724 1,058,359 Common stock available for the Employee Stock Purchase Plan 609,053 750,000 Total 6,748,609 5,987,880

Stock Incentive Plans (Tables)

Stock Incentive Plans (Tables)	12 Months Ended
	Dec. 31, 2016
Stock incentive plans
Summary of activity under the Company's stock option plans	The following table summarizes activity under the Company's stock incentive plans (aggregate intrinsic value in thousands): Shares Available for Grant Stock Options Weighted Weighted Average Aggregate Balance—December 31, 2015 1,058,359 4,179,521 $ 8.03 7.50 $ 6,511 Additional shares authorized 1,114,416 — Granted - stock options (1,618,250 ) 1,618,250 6.30 Granted - restricted stock units (25,000 ) 25,000 Canceled 358,199 (358,199 ) 10.29 Exercised — (212,740 ) 2.53 Balance—December 31, 2016 887,724 5,251,832 $ 7.56 7.24 $ 8,515 Options vested and exercisable—December 31, 2016 2,628,328 $ 7.42 5.89 $ 6,008 Options vested and expected to vest—December 31, 2016 4,962,370 $ 7.58 7.16 $ 8,254
Stock-based Compensation
Stock incentive plans
Summary of share-based compensation expense	The following table summarizes stock-based compensation expense related to stock options, restricted stock units and the ESPP for the years ended December 31, 2016, 2015 and 2014, and are included in the statements of operations and comprehensive loss as follows (in thousands of dollars): Year Ended December 31, 2016 2015 2014 Cost of revenue $ 126 $ 100 $ 51 Research and development 1,322 1,178 790 Selling and marketing 1,594 1,326 707 General and administrative 3,336 2,998 2,000 Total stock-based compensation expense $ 6,378 $ 5,602 $ 3,548
Stock-based Compensation, employees
Stock incentive plans
Schedule of assumptions used to calculate estimated grant date fair value of stock options using the Black-Scholes option-pricing valuation model	The estimated grant-date fair value of employee stock options was calculated using the Black-Scholes option-pricing model, based on the following assumptions: Year Ended December 31, 2016 2015 2014 Weighted-average volatility 52.49 - 56.36% 52.56 - 68.82% 70.19 - 78.54% Weighted-average expected term (years) 5.50 - 6.27 5.50 - 6.08 5.50 - 6.08 Risk-free interest rate 1.16 - 2.09% 1.55 - 2.03% 1.66 - 2.04% Expected dividend yield — — —
Stock-based Compensation, non-employees
Stock incentive plans
Schedule of assumptions used to calculate estimated grant date fair value of stock options using the Black-Scholes option-pricing valuation model	The estimated fair value of non-employee stock options was calculated using the Black-Scholes option-pricing model, based on the following assumptions: Year Ended December 31, 2016 2015 2014 Weighted-average volatility 52.77 - 65.85% 64.72 - 74.48% 73.20 - 74.48% Weighted-average expected term (years) 7.80 - 8.56 7.92 - 10.00 8.75 - 10.00 Risk-free interest rate 1.39 - 2.30% 1.78 - 2.29% 2.09 - 2.20% Expected dividend yield — — —
ESPP
Stock incentive plans
Schedule of assumptions used to calculate estimated grant date fair value of stock options using the Black-Scholes option-pricing valuation model	The estimated grant date fair value of the ESPP shares was calculated using the Black-Scholes option-pricing model, based on the following assumptions: Year Ended December 31, 2016 2015 Weighted-average volatility 46.38 - 75.72% 53.57 - 58.10% Weighted-average expected term (years) 0.50 - 1.00 0.49 - 0.99 Risk-free interest rate 0.40 - 0.50% 0.17 - 0.33% Expected dividend yield — —

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Schedule of reconciliation of tax expense computed at the statutory federal rate and the Company's tax expense	The following table presents a reconciliation of the tax expense computed at the statutory federal rate and the Company's tax expense for the periods presented (in thousands of dollars): Year Ended December, 31, 2016 2015 2014 U.S. federal taxes at statutory rate $ (10,662 ) $ (11,459 ) $ (9,987 ) State tax (net of federal benefit) 20 (30 ) 5 Permanent differences 153 96 64 Incentive stock options 1,095 789 672 Tax credits (677 ) (581 ) (461 ) Change in valuation allowance 10,071 11,185 9,707 Total $ — $ — $ —
Schedule of significant components of the Company's deferred tax assets and liabilities	Significant components of the Company's deferred tax assets and liabilities are as follows (in thousands of dollars): Year Ended December 31, 2016 2015 2014 Deferred tax assets: Net operating loss carryforwards $ 61,674 $ 52,262 $ 41,971 Research and development credits 3,174 2,497 1,916 Stock-based compensation 2,847 1,825 826 Genzyme co-promotion agreement — 330 995 Accruals, deferred rent and other 4,511 4,698 3,381 Gross deferred tax assets 72,206 61,612 49,089 Valuation allowance (65,975 ) (55,101 ) (43,439 ) Net deferred tax assets 6,231 6,511 5,650 Deferred tax liabilities: Property and equipment (1,180 ) (1,215 ) (60 ) In-process research and development (5,051 ) (5,296 ) (5,590 ) Gross deferred tax liabilities (6,231 ) (6,511 ) (5,650 ) Net deferred tax liabilities (6,231 ) (6,511 ) (5,650 ) Net deferred taxes $ — $ — $ —
Schedule of reconciliation of the beginning and ending amount of unrecognized tax benefits	A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows (in thousands of dollars): Year Ended December 31, 2016 2015 2014 Unrecognized tax benefits, beginning of period $ 1,871 $ 1,571 $ 727 Gross increases—tax position in prior period — — 548 Gross decreases—tax position in prior period — — — Gross increases—current period tax position 351 300 296 Lapse of statute of limitations — — — Unrecognized tax benefits, end of period $ 2,222 $ 1,871 $ 1,571

Selected Quarterly Financial 32

Selected Quarterly Financial Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Schedule of selected quarterly financial data (unaudited)	The results of operations for any quarter are not necessarily indicative of the results to be expected for any future period (in thousands of dollars, except for share and per share data): Quarter Ended March 31 June 30 September 30 December 31 2016: Revenue $ 13,550 $ 14,675 $ 18,603 $ 18,257 Net loss (10,075 ) (11,243 ) (5,637 ) (4,403 ) Net loss per common share, basic and diluted (0.36 ) (0.40 ) (0.20 ) (0.14 ) Shares used to compute net loss per common share, basic and diluted 27,817,993 27,859,918 27,916,819 31,705,603 2015: Revenue $ 11,218 $ 11,908 $ 12,335 $ 14,042 Net loss (7,610 ) (9,136 ) (8,945 ) (8,013 ) Net loss per common share, basic and diluted (0.34 ) (0.35 ) (0.32 ) (0.29 ) Shares used to compute net loss per common share, basic and diluted 22,539,723 26,048,934 27,640,806 27,672,806

Summary of Significant Accoun33

Summary of Significant Accounting Policies - Liquidity (Details) - USD ($) $ / shares in Units, $ in Thousands	Mar. 30, 2016	Nov. 30, 2016	Apr. 30, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Liquidity
Accumulated deficit				$ 180,084	$ 148,726
Cash and cash equivalents				$ 59,219	$ 39,084	$ 35,014	$ 71,220
Common stock, shares issued				33,762,278	27,685,291
Repayments of long-term debt				$ 5,000	$ 0	0
Net proceeds from sale of common stock in private placement				$ 0	$ 37,258	$ 0
Common Stock
Liquidity
Common stock, shares issued		5,723,300
Shares issued, price per share (in usd per share)		$ 6
Proceeds from issuance of common stock		$ 32,100
Payments of stock issuance costs		$ 2,200
Number of common stock issued and sold in private placement				5,723,300	4,907,975
Share Price (in usd per share)				$ 7.74	$ 7.20
Common Stock | Private placement
Liquidity
Number of common stock issued and sold in private placement			4,907,975
Share Price (in usd per share)			$ 8.15
Net proceeds from sale of common stock in private placement			$ 37,300
Agent fees and other expenses			$ 2,700
Line of Credit | Visium | Initial Term Loan
Liquidity
Proceeds from lines of credit	$ 25,000
Repayments of long-term debt	$ 5,000

Summary of Significant Accoun34

Summary of Significant Accounting Policies - Credit Risk, Restricted Cash, and Allowance for Doubtful Accounts (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2016USD ($)Institution	Dec. 31, 2015USD ($)	Dec. 31, 2014
Concentrations of Credit Risk and Other Risks and Uncertainties
Number of major financial institutions with which the company's cash and cash equivalents are deposited | Institution	1
Restricted Cash
Long term deposit consisting of letter of credit serving as security for lease	$ 603	$ 603
Headquarters and laboratory facilities, South San Francisco, Lease expiring 2016
Restricted Cash
Amount held as security for lease	120	118
Long term deposit consisting of letter of credit serving as security for lease		$ 603
Headquarters and laboratory facilities, South San Francisco, Lease signed in April 2015
Restricted Cash
Amount held as security for lease	603
Long term deposit consisting of letter of credit serving as security for lease	$ 603
Revenue | Revenue concentration risk
Concentrations of Credit Risk and Other Risks and Uncertainties
Concentrations of credit risk (as a percent)	47.00%	49.00%	55.00%
Revenue | Revenue concentration risk | Medicare
Concentrations of Credit Risk and Other Risks and Uncertainties
Concentrations of credit risk (as a percent)	27.00%	26.00%	26.00%
Revenue | Revenue concentration risk | United Healthcare
Concentrations of Credit Risk and Other Risks and Uncertainties
Concentrations of credit risk (as a percent)	12.00%	14.00%	18.00%
Revenue | Revenue concentration risk | Aetna
Concentrations of Credit Risk and Other Risks and Uncertainties
Concentrations of credit risk (as a percent)	8.00%	9.00%	11.00%
Accounts receivable | Gross receivables concentration risk | Medicare
Concentrations of Credit Risk and Other Risks and Uncertainties
Concentrations of credit risk (as a percent)	18.00%	31.00%
Accounts receivable | Gross receivables concentration risk | United Healthcare
Concentrations of Credit Risk and Other Risks and Uncertainties
Concentrations of credit risk (as a percent)	8.00%	25.00%
Accounts receivable | Gross receivables concentration risk | Aetna
Concentrations of Credit Risk and Other Risks and Uncertainties
Concentrations of credit risk (as a percent)	4.00%	23.00%

Summary of Significant Accoun35

Summary of Significant Accounting Policies - Intangible Assets, Bonus Accruals, and Revenue Recongition (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accounting Policies [Abstract]
Impairment of intangible assets, indefinite-lived (excluding goodwill)										$ 0
Finite-lived Intangible Assets
Useful life									15 years
Finite-lived intangible assets, impairment									$ 0
Goodwill
Goodwill impairment									0	0
Revenue Recognition
Revenue recognized on an accrual basis									$ 47,099,000	$ 27,043,000	$ 12,545,000
Revenue recognized on accrual basis, percentage									72.00%	55.00%	33.00%
Revenue recognized on a cash basis									$ 17,986,000	$ 22,460,000	$ 25,645,000
Revenue recognized on a cash basis, percentage									28.00%	45.00%	67.00%
Total	$ 18,257,000	$ 18,603,000	$ 14,675,000	$ 13,550,000	$ 14,042,000	$ 12,335,000	$ 11,908,000	$ 11,218,000	$ 65,085,000	$ 49,503,000	$ 38,190,000
Total, Percent									100.00%	100.00%	100.00%
Net loss per common share, basic and diluted (in dollars per share)	$ (0.14)	$ (0.20)	$ (0.40)	$ (0.36)	$ (0.29)	$ (0.32)	$ (0.35)	$ (0.34)	$ (1.09)	$ (1.30)	$ (1.36)
Accrued Income Receivable
Revenue Recognition
Total		$ 3,500,000							$ 4,100,000	$ 700,000	$ 800,000
Net loss per common share, basic and diluted (in dollars per share)									$ 0.13	$ 0.03	$ 0.04
Minimum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Property, plant and equipment, useful life (in years)									3 years
Maximum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Property, plant and equipment, useful life (in years)									5 years

Net Loss Per Share (Details)

Net Loss Per Share (Details) - shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Outstanding shares of common stock equivalents that have been excluded from diluted net loss per common share
Shares of common stock subject to outstanding options	5,155,105	4,102,201	3,035,614
Options
Outstanding shares of common stock equivalents that have been excluded from diluted net loss per common share
Shares of common stock subject to outstanding options	5,093,454	4,086,640	3,035,614
Employee stock purchase plan
Outstanding shares of common stock equivalents that have been excluded from diluted net loss per common share
Shares of common stock subject to outstanding options	36,651	15,561	0
Restricted stock units (RSUs)
Outstanding shares of common stock equivalents that have been excluded from diluted net loss per common share
Shares of common stock subject to outstanding options	25,000	0	0

Business Combination (Details)

Business Combination (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Sep. 16, 2014
Fair value of the assets acquired and liabilities assumed:
Goodwill		$ 1,057	$ 1,057
Useful life		15 years
Amortization of IPR&D		$ 1,067	800	$ 0
Pro-Forma Financial Information
Revenue			38,190	21,884
Net loss			(29,090)	(28,605)
Allegro
Business Combination
Number of Allegro shares received for each share of common stock issued and outstanding of a wholly-owned subsidiary of the Company	1
Conversion right, number of shares	964,377
Conversion right, cash	$ 2,700
Outstanding indebtedness settled in cash	4,300
Acquisition-related costs	500
Transaction bonuses and severance payments	1,200
Acquisition consideration
Stock	10,078
Cash	2,725
Payment of outstanding indebtedness	4,290
Total acquisition consideration	17,093
Closing price of Company's common stock					$ 10.45
Fair value of the assets acquired and liabilities assumed:
Cash and cash equivalents	29
Other assets, net	7
In-process research and development	16,000
Goodwill	1,057
Total acquisition consideration	$ 17,093
Discount rate (as a percent)	18.50%
Allegro | Transaction bonus and other payments to employees and acquisition related costs
Pro-Forma Financial Information
Net loss			2,200
Allegro | Interest expense related to indebtedness of acquired entity
Pro-Forma Financial Information
Net loss			2,300	$ 4,500
Allegro | IPR&D
Fair value of the assets acquired and liabilities assumed:
Accumulated amortization		1,100	800
Annual amortization expense expected to be recognized		1,900	$ 800
Amortization expense over each of the next five years		$ 1,100
Allegro | IPR&D | Maximum
Fair value of the assets acquired and liabilities assumed:
Useful life		15 years

Balance Sheet Components - Prop

Balance Sheet Components - Property and Equipment, Net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property and Equipment, Net
Total property and equipment, at cost	$ 18,316	$ 15,754
Accumulated depreciation and amortization	(6,836)	(5,440)
Total property and equipment, net	11,480	10,314
Depreciation and amortization expense	3,511	2,254	$ 1,175
Depreciation and amortization expense	2,400	1,500
Leasehold improvements
Property and Equipment, Net
Total property and equipment, at cost	5,861	789
Laboratory equipment
Property and Equipment, Net
Total property and equipment, at cost	6,441	5,501
Computer equipment
Property and Equipment, Net
Total property and equipment, at cost	1,177	1,046
Software, including software developed for internal use
Property and Equipment, Net
Total property and equipment, at cost	1,937	1,353
Furniture and fixtures
Property and Equipment, Net
Total property and equipment, at cost	1,131	242
Construction-in-process
Property and Equipment, Net
Total property and equipment, at cost	$ 1,769	$ 6,823

Balance Sheet Components - Accr

Balance Sheet Components - Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Accrued Liabilities
Accrued compensation expenses	$ 6,120	$ 4,212
Accrued Genzyme co-promotion fees	0	2,089
Accrued other	2,990	2,388
Total accrued liabilities	$ 9,110	$ 8,689

Fair Value Measurements (Detail

Fair Value Measurements (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Money Market Funds | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value disclosure	$ 58.7	$ 37.5

Commitments and Contingencies41

Commitments and Contingencies (Details) ft² in Thousands, $ in Thousands	1 Months Ended	12 Months Ended
	Apr. 30, 2015ft²	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Feb. 08, 2017USD ($)
Future minimum lease payments under non-cancelable operating leases
2,017		$ 2,143
2,018		2,102
2,019		2,026
2,020		2,082
2,021		2,144
Thereafter		9,812
Total minimum lease payments		20,309
Facilities rent expense		2,000	$ 1,900	$ 852
Supplies Purchase Commitments
Non-cancelable purchase commitment		1,700
Headquarters and laboratory facilities, South San Francisco, Lease signed in April 2015
Operating Leases
Amount of space leased | ft²	59
Security deposit		603
Laboratory facilities, Austin, Texas
Operating Leases
Security deposit		$ 75	$ 75
Subsequent event | Headquarters and laboratory facilities, South San Francisco, Lease signed in April 2015
Operating Leases
Lease Modification, Consideration Received					$ 500

Commitments and Contingencies C

Commitments and Contingencies Capital Lease (Details) - Equipment $ in Thousands	Dec. 31, 2016USD ($)
Capital Leased Assets [Line Items]
Capital leased assets	$ 1,200
Capital lease, upfront payment	330
Capital leases, future minimum payments, present value of net minimum payments	874
Future minimum payments due, 2017	317
Future minimum payments due, 2018	317
Future minimum payments due, 2019	317
Accrued Liabilities
Capital Leased Assets [Line Items]
Future minimum payments due	275
Capital Lease Obligations
Capital Leased Assets [Line Items]
Future minimum payments due	$ 599

Debt Credit Agreement (Details)

Debt Credit Agreement (Details)	Mar. 30, 2016USD ($)	Dec. 31, 2016USD ($)installmentloan	Dec. 31, 2016USD ($)installmentloan	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)
Debt Instrument [Line Items]
Repayments of long-term debt			$ 5,000,000	$ 0	$ 0
Conversion of accrued interest to long-term debt			$ 385,000	$ 0	$ 0
Visium | Line of Credit
Debt Instrument [Line Items]
Number of term loans | loan		2	2
Line of credit facility, maximum borrowing capacity		$ 40,000,000	$ 40,000,000
Interest rate, stated percentage		12.00%	12.00%
Number of installments | installment		8	8
Term of debt with equal quarterly installments			2 years
Fixed rate percentage paid in cash		0.090	0.090
Interest paid-in-kind percentage		0.030	0.030
Conversion of accrued interest to long-term debt		$ 385,000
Minimum prepayment allowed			$ 5,000,000
Prepayment amount excess multiple			$ 1,000,000
Penalty percentage on prepayment period one			0.240
Penalty percentage on prepayment period two			0.040
Penalty percentage on prepayment period three			0.020
Penalty percentage on prepayment period four			0.010
Period for which rights equity financings			1 year
Visium | Line of Credit | Maximum
Debt Instrument [Line Items]
Future equity financings amount		5,000,000	$ 5,000,000
Visium | Line of Credit | Initial Term Loan
Debt Instrument [Line Items]
Proceeds from lines of credit	$ 25,000,000
Repayments of long-term debt	$ 5,000,000
Visium | Line of Credit | Second Term Loan
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity		$ 15,000,000	$ 15,000,000

Debt Credit Agreement- Tabular

Debt Credit Agreement- Tabular (Details) - Line of Credit	Dec. 31, 2016USD ($)
Debt Instrument [Line Items]
Debt instrument, face amount	$ 25,385,000
Debt instrument, unamortized discount	(467,000)
Long-term debt	24,918,000
2,020	9,519,000
2,021	12,693,000
2,022	$ 3,173,000

Debt Loan and Security Agreemen

Debt Loan and Security Agreement (Details) $ / shares in Units, $ in Thousands	1 Months Ended				12 Months Ended
	Nov. 30, 2015USD ($)	Dec. 31, 2014USD ($)tranche	Mar. 31, 2014USD ($)shares	Jun. 30, 2013USD ($)installment$ / sharesshares	Dec. 31, 2016USD ($)installment	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)tranche	Dec. 01, 2014USD ($)	Nov. 30, 2014USD ($)
Debt Instrument [Line Items]
Debt instrument, increase (decrease), net				$ 5,000
Cash paid for interest on debt					$ 2,149	$ 278	$ 307
Term Loan
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity		$ 15,000		10,000			$ 15,000
Number of tranches | tranche		3					3
Debt instrument, increase (decrease), net				5,000
Debt instrument, unused borrowing capacity, amount		$ 5,000	$ 5,000				$ 5,000
Number of installments | installment					24
Period after which debt is repayable		24 months
Penalty percentage on prepayment within one year of origination		2.00%
Penalty percentage on prepayment within two years of origination		1.00%
Penalty percentage on prepayment after two years of origination		0.00%
Cash paid for interest on debt		$ 14
End of term payment amount								$ 110	$ 225
Payments of debt extinguishment costs		110
Prepayment premium									$ 75
Third party fee, amount paid		45
Term Loan | Term Loan Due 2017
Debt Instrument [Line Items]
Debt instrument, increase (decrease), net				$ 5,000
Number of installments | installment				30
Period after which debt is repayable				18 months
Interest rate, stated percentage				6.06%
Penalty percentage on prepayment within one year of origination				2.25%
Penalty percentage on prepayment within two years of origination				1.50%
Penalty percentage on prepayment after two years of origination				0.75%
Proceeds from (repayments of) debt		5,000
Term Loan | Term Loan Tranche One
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity		5,000					$ 5,000
Debt instrument, increase (decrease), net		5,000
Interest rate, stated percentage						5.00%
Term Loan | Term Loan Tranche Two
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity						$ 5,000
Debt instrument, increase (decrease), net	$ 5,000	$ 5,000
Term Loan | Term Loan Tranche Three
Debt Instrument [Line Items]
Debt instrument, increase (decrease), net	$ 5,000
Convertible Preferred Stock Warrants
Debt Instrument [Line Items]
Class of warrant or right, exercise price of warrants or rights | $ / shares				$ 7.56
Class of warrant or right, number of securities for which warrants will become exercisable in event of conversion of preferred stock into common stock | shares				24,801
Fair value of liability				$ 175
Remaining discount amortization period				48 months
Issuance of common stock on cashless exercise of warrant (in shares) | shares			13,739

Debt Loan and Security Agreem46

Debt Loan and Security Agreement- Tabular (Details) - Term Loan $ in Thousands	Dec. 31, 2015USD ($)
Debt Instrument [Line Items]
Long-term debt and accrued end of term payment	$ 5,082
Debt instrument, unamortized discount	92
Long-term debt	$ 4,990

Interest Expense (Details)

Interest Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Interest Expense, Debt [Abstract]
End-of-term payment	$ 206	$ 79	$ 81
Term Loan
Interest Expense, Debt [Abstract]
Nominal interest	2,378	253	296
Amortization of debt discount and debt issuance costs	173	46	62
End-of-term payment	206	79	81
Total	$ 2,757	$ 378	$ 439

Stockholders' Equity (Details)

Stockholders' Equity (Details)	1 Months Ended			12 Months Ended
	Nov. 30, 2016USD ($)$ / sharesshares	May 31, 2015USD ($)	Apr. 30, 2015USD ($)$ / sharesshares	Dec. 31, 2016USD ($)vote$ / sharesshares	Dec. 31, 2015USD ($)$ / sharesshares	Dec. 31, 2014USD ($)
Common Stock
Authorized shares of common stock				125,000,000	125,000,000
Par value of shares of common stock (in dollars per share) | $ / shares				$ 0.001	$ 0.001
Number of votes for each share of stock | vote				1
Dividends declared | $				$ 0
Options issued and outstanding (in shares)				5,251,832	4,179,521
Shares available for issuance				887,724	1,058,359
Total number of shares reserved for issuance				6,748,609	5,987,880
Common stock, shares issued				33,762,278	27,685,291
Net proceeds from sale of common stock in private placement | $				$ 0	$ 37,258,000	$ 0
Options
Common Stock
Options issued and outstanding (in shares)				5,251,832	4,179,521
Shares available for issuance				887,724	1,058,359
ESPP
Employee Stock Purchase Plan
Maximum offering period		12 months
Purchase period		6 months
Maximum fair market value of shares an employee can purchase per calendar year | $		$ 25,000
Assumptions used to calculate estimated fair value of stock options using the Black-Scholes option-pricing valuation model
Weighted-average volatility, low end of range (as a percent)				46.38%	53.57%
Weighted-average volatility, high end of range (as a percent)				75.72%	58.10%
Risk-free interest rate, low end of range (as a percent)				0.40%	0.17%
Risk-free interest rate, high end of range (as a percent)				0.50%	0.33%
ESPP | Minimum
Employee Stock Purchase Plan
Minimum purchase price as a percentage of fair market value		85.00%
Assumptions used to calculate estimated fair value of stock options using the Black-Scholes option-pricing valuation model
Weighted-average expected term				6 months	5 months 27 days
ESPP | Maximum
Assumptions used to calculate estimated fair value of stock options using the Black-Scholes option-pricing valuation model
Weighted-average expected term				1 year	11 months 27 days
Common Stock
Common Stock
Common stock, shares issued	5,723,300
Shares issued, price per share (in usd per share) | $ / shares	$ 6
Sale of stock, consideration received on transaction, gross | $	$ 34,300,000
Proceeds from issuance of common stock | $	32,100,000
Payments of stock issuance costs | $	$ 2,200,000
Number of common stock issued and sold in private placement				5,723,300	4,907,975
Share Price (in usd per share) | $ / shares				$ 7.74	$ 7.20
Common Stock | Private placement
Common Stock
Number of common stock issued and sold in private placement			4,907,975
Share Price (in usd per share) | $ / shares			$ 8.15
Gross proceeds from sale of common stock in private placement | $			$ 40,000,000
Net proceeds from sale of common stock in private placement | $			37,300,000
Agent fees and other expenses | $			$ 2,700,000
Common Stock | ESPP
Common Stock
Shares available for issuance				609,053	750,000
Prepaid Expenses and Other Current Assets
Common Stock
Accounts receivable | $				$ 200,000

Stock Incentive Plans - Stock O

Stock Incentive Plans - Stock Option Plans (Details) - shares	1 Months Ended	12 Months Ended
	Feb. 29, 2008	Dec. 31, 2016	Dec. 31, 2015	Oct. 31, 2013
Stock incentive plans
Number of shares available for issuance		887,724	1,058,359
Options
Stock incentive plans
Number of shares available for issuance		887,724	1,058,359
2008 Plan | Options | Minimum
Stock incentive plans
Minimum purchase price as a percentage of fair market value	100.00%
2008 Plan | Options | Maximum
Stock incentive plans
Term of options granted	10 years
2008 Plan | ISO | Minimum
Stock incentive plans
Voting power of person owning stock (as a percent)	10.00%
Option price as a percentage of estimated fair value of shares on date of grant to a person owning stock representing more than 10% of voting power of all classes of stock	110.00%
2008 Plan | ISO | Maximum
Stock incentive plans
Term of options granted to a person owning stock representing more than 10% of voting power of all classes of stock	5 years
Stock Incentive Plan2013 [Member]
Stock incentive plans
Number of additional shares reserved for issuance				1,700,000
Maximum annual increase in outstanding shares on the last day of the immediately preceding fiscal year (as a percent)		4.00%
Number of shares available for issuance		887,724
Stock Incentive Plan2013 [Member] | Options | Outside director serving as a member of Board of Directors for at least six months
Stock incentive plans
Shares granted as annual grant		10,000
Stock Incentive Plan2013 [Member] | Options | Outside director serving as a member of Board of Directors for at least six months | Minimum
Stock incentive plans
Period for which director has to serve as board of director to receive grant to purchase shares		6 months
Stock Incentive Plan2013 [Member] | Options | Outside director
Stock incentive plans
Minimum purchase price as a percentage of fair market value		100.00%
Stock Incentive Plan2013 [Member] | Options | Outside director | Maximum
Stock incentive plans
Expiration period after termination of service		12 months
Stock Incentive Plan2013 [Member] | ISO | Maximum
Stock incentive plans
Minimum purchase price as a percentage of fair market value		100.00%
Stock Incentive Plan2013 [Member] | NSO | Minimum
Stock incentive plans
Minimum purchase price as a percentage of fair market value		100.00%
Stock Incentive Plan2013 [Member] | NSO | Outside director who was not previously an employee
Stock incentive plans
Percentage of award vesting after one year		25.00%
Shares granted as initial grant		35,000
Percentage of award granted which vests on a monthly basis		0.75
Period over which remaining shares will vest on a monthly basis		3 years

Stock Incentive Plans - Activit

Stock Incentive Plans - Activity Under Stock Option Plans (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Shares Available for Grant
Balance at the beginning of the period (in shares)	1,058,359
Additional options authorized (in shares)	1,114,416
Canceled (in shares)	358,199
Balance at the end of the period (in shares)	887,724	1,058,359
Stock Options Outstanding
Balance at beginning of the period (in shares)	4,179,521
Canceled (in shares)	(358,199)
Exercised (in shares)	(212,740)
Balance at the end of the period (in shares)	5,251,832	4,179,521
Options vested and exercisable at the end of the period (in shares)	2,628,328
Options vested and expected to vest at the end of the period (in shares)	4,962,370
Weighted Average Exercise Price
Balance at beginning of the period (in dollars per share)	$ 8.03
Canceled (in dollars per share)	10.29
Exercised (in dollars per share)	2.53
Balance at the end of the period (in dollars per share)	7.56	$ 8.03
Options vested and exercisable at the end of the period (in dollars per share)	7.42
Options vested and expected to vest at the end of the period (in dollars per share)	$ 7.58
Weighted Average Remaining Contractual Life
Balance	7 years 2 months 26 days	7 years 6 months
Options vested and exercisable at the end of the period	5 years 10 months 20 days
Options vested and expected to vest at the end of the period	7 years 1 month 27 days
Aggregate Intrinsic Value
Balance at the beginning of the period (in dollars)	$ 6,511
Balance at the end of the period (in dollars)	8,515	$ 6,511
Options vested and exercisable at the end of the period (in dollars)	6,008
Options vested and expected to vest at the end of the period (in dollars)	$ 8,254
Employee stock options
Shares Available for Grant
Granted (in shares)	(1,618,250)
Stock Options Outstanding
Granted (in shares)	1,618,250
Weighted Average Exercise Price
Granted (in dollars per share)	$ 6.30
Restricted stock units (RSUs)
Shares Available for Grant
Granted (in shares)	(25,000)
Stock Options Outstanding
Granted (in shares)	25,000

Stock Incentive Plans - Additio

Stock Incentive Plans - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Stock incentive plans
Weighted average fair value of options to purchase common stock granted (in dollars per share)	$ 3.35	$ 5.12	$ 9.08
Intrinsic value of stock options exercised (in dollars)	$ 0.9	$ 1.8	$ 3.2
Weighted average grant date fair value (in usd per share)	$ 7.47
Common Stock
Stock incentive plans
Share Price (in usd per share)	$ 7.74	$ 7.20
Employee stock options
Stock incentive plans
Total estimated grant date fair value of options to purchase common stock vested (in dollars)	$ 5.8	$ 5.3	$ 1.6

Stock Incentive Plans Stock Inc

Stock Incentive Plans Stock Incentive Plans- ESPP (Details) - ESPP	1 Months Ended
	May 31, 2015USD ($)
Stock incentive plans
Maximum offering period	12 months
Purchase period	6 months
Maximum fair market value of shares an employee can purchase per calendar year	$ 25,000
Minimum
Stock incentive plans
Minimum purchase price as a percentage of fair market value	85.00%

Stock Incentive Plans - Stock-b

Stock Incentive Plans - Stock-based Compensation (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Feb. 29, 2008	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Stock-based Compensation
Stock-based compensation
Share-based compensation expense (in dollars)		$ 6,378	$ 5,602	$ 3,548
Unrecognized compensation expense (in dollars)		$ 9,300
Period over which unrecognized compensation expense expected to be recognized		2 years 6 months
Stock-based Compensation | Cost of revenue
Stock-based compensation
Share-based compensation expense (in dollars)		$ 126	100	51
Stock-based Compensation | Research and development
Stock-based compensation
Share-based compensation expense (in dollars)		1,322	1,178	790
Stock-based Compensation | Selling and marketing
Stock-based compensation
Share-based compensation expense (in dollars)		1,594	1,326	707
Stock-based Compensation | General and administrative
Stock-based compensation
Share-based compensation expense (in dollars)		$ 3,336	$ 2,998	$ 2,000
Stock-based Compensation, employees
Assumptions used to calculate estimated fair value of stock options using the Black-Scholes option-pricing valuation model
Weighted-average volatility, low end of range (as a percent)		52.49%	52.56%	70.19%
Weighted-average volatility, high end of range (as a percent)		56.36%	68.82%	78.54%
Risk-free interest rate, low end of range (as a percent)		1.16%	1.55%	1.66%
Risk-free interest rate, high end of range (as a percent)		2.09%	2.03%	2.04%
Stock-based Compensation, non-employees
Assumptions used to calculate estimated fair value of stock options using the Black-Scholes option-pricing valuation model
Weighted-average volatility, low end of range (as a percent)		52.77%	64.72%	73.20%
Weighted-average volatility, high end of range (as a percent)		65.85%	74.48%	74.48%
Risk-free interest rate, low end of range (as a percent)		1.39%	1.78%	2.09%
Risk-free interest rate, high end of range (as a percent)		2.30%	2.29%	2.20%
ESPP
Assumptions used to calculate estimated fair value of stock options using the Black-Scholes option-pricing valuation model
Weighted-average volatility, low end of range (as a percent)		46.38%	53.57%
Weighted-average volatility, high end of range (as a percent)		75.72%	58.10%
Risk-free interest rate, low end of range (as a percent)		0.40%	0.17%
Risk-free interest rate, high end of range (as a percent)		0.50%	0.33%
Minimum | Stock-based Compensation, employees
Assumptions used to calculate estimated fair value of stock options using the Black-Scholes option-pricing valuation model
Weighted-average expected term		5 years 6 months	5 years 6 months	5 years 6 months
Minimum | Stock-based Compensation, non-employees
Assumptions used to calculate estimated fair value of stock options using the Black-Scholes option-pricing valuation model
Weighted-average expected term		7 years 9 months 18 days	7 years 11 months 1 day	8 years 9 months
Minimum | ESPP
Assumptions used to calculate estimated fair value of stock options using the Black-Scholes option-pricing valuation model
Weighted-average expected term		6 months	5 months 27 days
Maximum | Stock-based Compensation, employees
Assumptions used to calculate estimated fair value of stock options using the Black-Scholes option-pricing valuation model
Weighted-average expected term		6 years 3 months 7 days	6 years 29 days	6 years 29 days
Maximum | Stock-based Compensation, non-employees
Assumptions used to calculate estimated fair value of stock options using the Black-Scholes option-pricing valuation model
Weighted-average expected term		8 years 6 months 22 days	10 years	10 years
Maximum | ESPP
Assumptions used to calculate estimated fair value of stock options using the Black-Scholes option-pricing valuation model
Weighted-average expected term		1 year	11 months 27 days
2008 Plan | Maximum | Options
Stock-based compensation
Term of options granted	10 years
2008 Plan | Maximum | ISO
Stock-based compensation
Term of options granted to a person owning stock representing more than 10% of voting power of all classes of stock	5 years

Genzyme Co-promotion Agreement

Genzyme Co-promotion Agreement (Details) $ in Thousands

Jan. 01, 2015

Aug. 12, 2014

Feb. 29, 2012USD ($)

Feb. 29, 2008USD ($)

Dec. 31, 2016USD ($)

Dec. 31, 2015USD ($)

Dec. 31, 2014USD ($)

Dec. 31, 2012

Feb. 27, 2014

Dec. 31, 2015USD ($)

Aug. 11, 2014

Feb. 28, 2015country

Jan. 31, 2012country

Genzyme Co-promotion Agreement

Amortization of up-front co-promotion fee

$ 948

$ 1,897

$ 2,269

Co-promotion agreement | Genzyme

Genzyme Co-promotion Agreement

Co-promotion expenses

6,100

7,300

12,000

Outstanding obligation to Genzyme

0

2,100

$ 2,100

Amortization of up-front co-promotion fee

$ 900

$ 1,900

$ 2,300

Afirma thyroid diagnostic solution co-promotion agreement | Genzyme

Genzyme Co-promotion Agreement

Number of countries outside United States for exclusive promotion under the agreement | country

40

Co-promotion fee received from Genzyme

$ 10,000

$ 10,000

Co-promotion fees as a percentage of cash receipts

15.00%

50.00%

40.00%

32.00%

Straight-line amortization period of co-promotion fee

4 years

Termination notification period

6 months

Ex-U.S. Co-Promotion Agreement | Genzyme

Genzyme Co-promotion Agreement

Number of countries outside United States for exclusive promotion under the agreement | country

5

Co-promotion fee paid as a percentage of net revenue

25.00%

Period of agreement

5 years

Thyroid Cytopathology Partners

Thyroid Cytopathology Partners (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Thyroid Cytopathology Partners
Outstanding obligations	$ 2,424	$ 5,085
Thyroid Cytopathology Partners
Thyroid Cytopathology Partners
Notice of intent not to renew period	12 months
Expenses for cytopathology testing and evaluation services	$ 5,100	4,700	$ 4,000
Outstanding obligations	426	820
Reduction to rent expense for TCP's portion of costs for shared space	$ (103)	$ (90)	$ (86)

Income Taxes - Tax Effects (Det

Income Taxes - Tax Effects (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Pretax loss	$ 31,400	$ 33,700	$ 29,400
Provision for income taxes	0	0	0
Reconciliation of tax expense computed at the statutory federal rate and the Company's tax expense
U.S. federal taxes at statutory rate	(10,662)	(11,459)	(9,987)
State tax (net of federal benefit)	20	(30)	5
Permanent differences	153	96	64
Incentive stock options	1,095	789	672
Tax credits	(677)	(581)	(461)
Change in valuation allowance	10,071	11,185	9,707
Total provision for income taxes	0	0	0
Non-current deferred tax assets:
Net operating loss carryforwards	61,674	52,262	41,971
Research and development credits	3,174	2,497	1,916
Stock-based compensation	2,847	1,825	826
Genzyme co-promotion agreement	0	330	995
Accruals, deferred rent and other	4,511	4,698	3,381
Gross deferred tax assets	72,206	61,612	49,089
Valuation allowance	(65,975)	(55,101)	(43,439)
Net deferred tax assets	6,231	6,511	5,650
Deferred tax liabilities:
Property and equipment	(1,180)	(1,215)	(60)
In-process research and development	(5,051)	(5,296)	(5,590)
Gross deferred tax liabilities	(6,231)	(6,511)	(5,650)
Net deferred tax liabilities	(6,231)	(6,511)	(5,650)
Increase in valuation allowance against deferred tax assets	10,900	$ 11,700	$ 10,600
Operating loss carryforwards
Federal and state net operating loss carryforwards related to stock-based compensation	1,600
Federal
Operating loss carryforwards
Net operating loss carryforwards	169,100
State
Operating loss carryforwards
Net operating loss carryforwards	$ 84,200

Income Taxes - Unrecognized Tax

Income Taxes - Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Reconciliation of the beginning and ending amount of unrecognized tax benefits
Unrecognized tax benefits, beginning of period	$ 1,871	$ 1,571	$ 727
Gross increases-tax position in prior period		0	548
Gross increases-current period tax position	351	300	296
Unrecognized tax benefits, end of period	2,222	$ 1,871	$ 1,571
Interest expense or penalties related to unrecognized tax benefits	0
Federal
Credit carryforwards
Credit carryforwards available to reduce future taxable income	3,300
State
Credit carryforwards
Credit carryforwards available to reduce future taxable income	$ 2,700

Income Taxes - Income Tax Exami

Income Taxes - Income Tax Examination (Details)	12 Months Ended
	Dec. 31, 2016
Federal
Income tax examination
Income tax examination period	3 years
State
Income tax examination
Income tax examination period	4 years

401(k) Plan (Details)

401(k) Plan (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Compensation and Retirement Disclosure [Abstract]
Employer contributions to the plan	$ 262,000	$ 103,000	$ 0

Selected Quarterly Financial 60

Selected Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Selected Quarterly Financial Data (Unaudited)
Total revenues	$ 18,257	$ 18,603	$ 14,675	$ 13,550	$ 14,042	$ 12,335	$ 11,908	$ 11,218	$ 65,085	$ 49,503	$ 38,190
Net loss	$ (4,403)	$ (5,637)	$ (11,243)	$ (10,075)	$ (8,013)	$ (8,945)	$ (9,136)	$ (7,610)	$ (31,358)	$ (33,704)	$ (29,373)
Net loss per common share, basic and diluted	$ (0.14)	$ (0.20)	$ (0.40)	$ (0.36)	$ (0.29)	$ (0.32)	$ (0.35)	$ (0.34)	$ (1.09)	$ (1.30)	$ (1.36)
Shares use to compute net loss per common share, basic and diluted (in shares)	31,705,603	27,916,819	27,859,918	27,817,993	27,672,806	27,640,806	26,048,934	22,539,723	28,830,472	25,994,193	21,639,374