Background/aim: To investigate the reliability of fine-needle aspiration biopsy (FNAB) in thyroid nodules and benign/malignant discrimination, particularly in large nodules. Materials and methods:A retrospective analysis of 1466 nodules in 402 patients with thyroid nodules who underwent thyroid surgery was made. The pathologic results of the thyroid nodules from preoperative FNAB and postoperative surgical pathology results were compared.Results: FNAB was found to be in accordance with the postoperative pathologic results. A concordance between the FNAB and postoperative pathologic results, particularly in nodules less than 3 cm in size, was detected. However, a similar finding was not detected in nodules larger than 3 cm in size. The rates, calculated without taking into consideration the nodule dimensions, were found to be: sensitivity, 47.65%; specificity, 93.98%; false-negative, 52.35%; and false-positive 6.02% Conclusion:In our experience, the false-negative rate of FNAB in nodules larger than 3 cm was high. Therefore, we have concluded that in the event of malignant FNAB, this rate is significant; however, in the event of benign FNAB, it should not be trusted too much.

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