Molecular testing raises thyroid nodule fine needle aspiration diagnostic value

Thyroid fine needle aspiration biopsy (FNAB) remains indeterminate in 16–24% of the cases. Molecular testing could improve the diagnostic accuracy of FNAB. This study examined the gene mutation profile of patients with thyroid nodules and analyzed the diagnostic ability of molecular testing for thyroid nodules using a self-developed 18-gene test. Between January 2019 and August 2021, 513 samples (414 FNABs and 99 formalin-fixed paraffin-embedded (FFPE) specimens) underwent molecular testing at Ruijin Hospital. Sensitivity (Sen), specificity (Spe), positive predictive value (PPV), negative predictive value (NPV), and accuracy were calculated. There were 457 mutations in 428 samples. The rates of BRAF, RAS, TERT promoter, RET/PTC, and NTRK3 fusion mutations were 73.3% (n = 335), 9.6% (n = 44), 2.8% (n = 13), 4.8% (n = 22), and 0.4% (n = 2), respectively. The diagnostic ability of cytology and molecular testing were evaluated in Bethesda II and V–VI samples. For cytology alone, Sen, Spe, PPV, NPV, and accuracy were 100%, 25.0%, 97.4%, 100%, and 97.4%; these numbers were 87.5%, 50.0%, 98.0%, 12.5%, and 86.2% when considering positive mutation, and 87.5%, 75.0%, 99.0%, 17.6%, and 87.1% when considering positive cytology or and positive mutation. In Bethesda III–IV nodules, when relying solely on the presence of pathogenic mutations for diagnosis, Sen, Spe, PPV, NPV, and AC were 76.2%, 66.7%, 94.1%, 26.8%, and 75.0%, respectively. It might be necessary to analyze the molecular mechanisms of disease development at the genetic level to predict patients with malignant nodules more accurately in different risk strata and develop rational treatment strategies and definite management plans.