ThyroSeq v3 for Bethesda III and IV: An institutional experience.

BACKGROUND: The ThyroSeq v3 genomic classifier is a commercial molecular test that examines a wide spectrum of genomic alterations in a thyroid fine-needle aspiration (FNA) sample and reports test results as either negative or positive. The authors report their institutional experience with ThyroSeq v3. METHODS: Thyroid FNA specimens diagnosed as either atypia of undetermined significance or follicular lesion of undetermined significance (AUS/FLUS) (Bethesda category III [Bethesda III] according to The Bethesda System for Reporting Thyroid Cytopathology) or follicular neoplasm/suspicious for follicular neoplasm (FN/SFN) (Bethesda IV) that had ThyroSeq v3 results available from December 2017 through October 2019 were retrieved for analysis. FNA diagnoses were correlated with ThyroSeq v3 results and follow-up histopathology. RESULTS: In total, 415 cases (AUS/FLUS, n = 251; FN/SFN, n = 164) were retrieved: 294 (71%) were reported as ThyroSeq v3-negative, and 121 (29%) were reported as ThyroSeq v3-positive. The benign call rate (BCR) of ThyroSeq v3 for AUS/FLUS (82%; 206 of 251 cases) was significantly higher (P < .001) than that for FN/SFN (BCR, 54%; 88 of 164 cases). Histopathologic follow-up was available for 127 cases (ThyroSeq v3-positive, 96; ThyroSeq v3-negative, 31), of which 57 were benign and 70 were malignant (including noninvasive follicular thyroid neoplasm with papillary-like nuclear features). The negative predictive value of ThyroSeq v3 was significantly higher for AUS/FLUS (99.5%) than for FN/SFN (95.4%; P < .0294), given malignancy rates of 10% for AUS/FLUS and 30% for FN/SFN. Forty-five unique combinations of genetic alterations were detected in the operated ThyroSeq-positive cases, and there were only 5 false-negative cases, comprised of 4 low-risk neoplasms. CONCLUSIONS: The high BCR of ThyroSeq v3 for AUS/FLUS prevents surgery in a majority of patients. The ThyroSeq v3 genomic classifier reveals the complexity of the genetic signature of indeterminate nodules.