Diagnostic accuracy and importance of Fine Needle Aspiration Cytology in the prediction of malignancy in thyroid nodules

Objective: Since thyroid nodules have low malignant potential and thyroid cancers progress slowly, early diagnosis is important for a longer life expectancy. Fine needle aspiration (FNA) is a cost-effective method with an easy application, low complication rate and high diagnostic value. The aim of this study is to assess the diagnosis accuracy and prevalence of thyroid cancer by comparing the findings of FNA procedures performed in our center with definitive histopathology results of patients undergoing surgery after FNA and then comparing these results to the literature. Materials and Methods: Cytology reports of 1040 patients who underwent thyroid FNA between January 2021 and October 2022 were retrospectively evaluated. Definitive histopathology results of 146 patients who underwent total or subtotal thyroidectomy were compared with preoperative FNA cytology results. Thyroid cytological results were classified according to the 2017 Bethesda system diagnostic categories. Results: Cases with definitive histopathology results indicating malignancy accounted for 33.3% of non-diagnostic cases, 14.5% of benign, 18.5% of atypia or follicular lesion of undetermined significance (AUS)/FLUS, 33.3% of follicular neoplasm or suspected follicular neoplasm, 75.0% of suspected malignancy and 100% of malignant preoperative FNAC results. For malignant cases, FNA had a sensitivity of 47.5%, specificity of 98.1%, false-positive rate of 20.8%, false-negative rate of 17.2%, positive predictive value of 79.1%, negative predictive value of 82.8% and accuracy rate of 72.8%. Conclusion: In this study, the prevalence of thyroid cancer exceeded the cancer rates predicted by the 2017 Bethesda classification. Thyroid cancer may be predicted by the follow-up of patients with solitary or multiple nodules without a surgical indication, and a repeat FNA when necessary.