Afirma gene expression classifier (GEC) performed for indeterminate thyroid nodules

The Afirma Gene Expression Classifier (GEC) is commonly used to manage indeterminate nodules and to avoid unnecessary surgery. We report our experience with 49 GEC results and correlate with ultrasound characteristics and final surgical pathological diagnosis. Retrospective analysis of data on patients with indeterminate fine needle aspiration (FNA) results and subsequent GEC testing from 01/01/2014 to 12/31/2017. Ninety eight patients (89% women) with a mean age 57.1-1.2 years with 104 indeterminate nodules were included in the analysis. Of the 58 atypia of undetermined significance (AUS) at the first biopsy, repeat FNA was non-diagnostic in 4 (ND; 7%), 28 were benign (48%), 24 were AUS (41%), and one each was follicular neoplasm (FN; 2%) and malignant (2%). Of the 28 FN on the first biopsy, repeat FNA was ND in 2 (7%), 9 were benign (32%), 16 AUS (57%), and 1 FN (4%). Of the 49/104 (47%) who had GEC testing, 17 (35%) were benign and was suspicious in 32 (65%). Surgery was ultimately performed in 18 of the 49 GEC tested patients. The final pathology was benign in 6 (33%), 1 follicular thyroid cancer (FTC; 6%), 7 follicular variant of papillary thyroid cancer (FVPTC; 39%), and 4 non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) (22%). The most common cancer was FVPTC. Three of the 6 benign nodules (50%) had low or very low suspicious features of ATA sonographic pattern, while 8/12 (67%) malignant nodules had intermediate or high suspicious ATA features. The prevalence of malignancy in GEC suspicious nodules was 44% without and 66% with NIFTP. ATA ultrasound features would have avoided surgery in 6 benign nodules, but would miss 4 cancers. GEC avoided surgery in 17/49 (34%) patients. Bethesda-III nodules harbored low risk thyroid cancers, a conservative approach of these nodules with serial neck ultrasound assessment seems reasonable. We lack long term outcome data of GEC benign nodules, such patients should be monitored closely