Conclusions

This study found that FNAC and USG TI-RADS provided differing and potentially complementary preoperative information. In this surgically verified cohort, Bethesda V/VI FNAC showed 100% specificity and PPV, although these estimates had wide confidence intervals; its limited sensitivity reflected the recognized cytological challenges of follicular-patterned neoplasms and NIFTP. USG TI-RADS offered higher sensitivity with somewhat lower specificity, and both modalities showed moderate agreement with histopathology; thyroid functional status showed no independent association with malignancy. Follicular-patterned lesions, including FTC and NIFTP, were the most diagnostically challenging entities overall. Within the surgically verified subgroup, these findings support the complementary use of FNAC and USG TI-RADS in preoperative assessment. Larger prospective studies with more complete reference-standard verification are needed before the reported diagnostic-performance estimates can be generalized to all patients with thyroid nodules.