Application of fine-needle aspiration biopsy combined with multi-gene testing in the differential diagnosis of benign and malignant C-TIRADS 4 thyroid nodules

Aim To explore the clinical value of fine-needle aspiration biopsy (FNAB) combined with multi-gene testing (including BRAF V600E , TERT, RAS, and RET/PTC) in the differential diagnosis of benign and malignant thyroid Chinese Thyroid Imaging Reporting and Data System (C-TIRADS) 4 nodules and to compare its diagnostic performance with FNAB combined with single-gene testing. Methods A total of 650 patients (650 nodules) with thyroid nodules who visited our hospital between January 2021 and December 2024 were included in this study. All patients underwent ultrasound-guided FNAB and multi-gene testing (including BRAF V600E , TERT, RAS, and RET/PTC). Using postoperative pathological findings as the “gold standard,” the diagnostic performance of ultrasound-guided FNAB and multi-gene testing for C-TIRADS 4 thyroid nodules was analyzed. The diagnostic efficacy of FNAB alone, each single-gene test alone, multi-gene testing alone, FNAB combined with each single-gene test, and FNAB combined with multi-gene testing in differentiating benign from malignant C-TIRADS 4 thyroid nodules was evaluated using receiver operating characteristic curves. Results Among the 650 thyroid nodules, 432 were malignant, and 218 were benign according to postoperative pathology reports. FNAB combined with multi-gene testing demonstrated improved sensitivity compared with FNAB alone, with a sensitivity of 91.0%, specificity of 76.15%, and accuracy of 86.0%. The AUC of the combined method was 0.836, which was significantly higher than that of FNAB alone (0.781) and multi-gene testing alone (0.806) ( P < 0.05). In FNAB-indeterminate nodules, FNAB combined with multi-gene testing achieved a sensitivity of 88.24% and specificity of 89.19%. In the sensitivity analysis reclassifying Bethesda IV as FNAB-positive, FNAB alone achieved a sensitivity of 83.6%, specificity of 62.8%, and accuracy of 76.6%, confirming that the combined testing strategy provided incremental diagnostic value. Conclusion FNAB combined with multi-gene testing significantly improves the sensitivity for differentiating benign from malignant thyroid C-TIRADS 4 nodules. Compared with FNAB combined with single-gene BRAF V600E testing, the multi-gene testing strategy offers improved sensitivity, particularly for detecting BRAF V600E -negative malignancies and FNAB-indeterminate nodules.