Fine-needle aspiration cytology (FNAC) is the gold standard to diagnose thyroid nodules but fails in discriminating the nature of indeterminate lesions. Molecular testing can improve the diagnosis of these nodules and next-generation sequencing (NGS) can be used to test many genes simultaneously. Assess the performance of an NGS 17-gene panel on thyroid indeterminate FNAC. One hundred five indeterminate FNACs, 30.5% high-risk (TIR3B) and 69.5% low-risk (TIR3A), were analyzed by NGS. For TIR3A, the rate of mutated samples was 10.9%, significantly lower (p = 0.0001) compared to TIR3B (63.6%). Twenty-two mutated and fourteen non-mutated samples were submitted to surgery. At histology, the overall malignancy was 85.7% in the indeterminate group that had a positive molecular test and 13.3% in the mutation-negative (p = 0.01). The 17-gene panel had a sensitivity of 90%, specificity of 87%, positive predictive value (PPV) of 91%, and negative predictive value (NPV) of 87%. We reported the utility of Ultrasound Malignancy Risk Stratification of Thyroid Nodules in Adults (EU-TIRADS) in selecting indeterminate nodules for molecular analysis, showing a significant correlation between US score and mutation (p = 0.004). The performance of a 17-gene panel based on NGS technology is promising, allowing the selection of indeterminate nodules to submit to surgery with a great specificity and PPV.
Keywords: cytology; indeterminate thyroid nodules; next-generation sequencing.