Incidental thyroid carcinoma: Correlation between FNAB cytology and pathological examination in 1093 cases

Objective: To investigate Incidental Thyroid Carcinoma (ITC) by comparing the results of Fine Needle Aspiration Biopsy (FNAB) cytology and the postoperative pathological findings. Methods: Data of 1479 patients who underwent total thyroidectomy were retrieved. Three hundred eighty-six patients were excluded due to insufficient data. Each surgical specimen studied received two histopathological diagnoses: the local diagnosis - for the same area in which the FNAB was performed; and the final diagnosis, which includes a study of the entire surgical specimen. Results: A thousand and ninety-three patients were investigated. FNAB result was malignant in 187 patients, benign in 204, suspicious or indeterminate in 668 cases, and inconclusive in 34 cases. The prevalence of ITC was 15.1%. Most of the ITC in this series was less than 0.5 cm. The incidence of ITC was higher in Bethesda III (17.5% ITC) and IV (19% ITC) than in Bethesda II cases (1.5% false negatives and 9% ITC). Conclusion: Although the incidence of false-negative results in Bethesda II nodules is only 1.5%, 9% of these patients had ITC in the thyroid parenchyma outside the nodule that underwent preoperative FNAB. The incidence of ITC in the same scenario was even higher in Bethesda III (17.5%) and Bethesda IV cases (19%). Ultrasonography-guided FNAB is an excellent method for the assessment of thyroid nodules. However, biopsy sites should be carefully selected. Despite the high incidence of incidentalomas, total thyroidectomy should not always be the treatment of choice due to its rare but potentially serious complications. The findings of the present study can assist future clinical decisions towards active surveillance strategies for the management of papillary thyroid carcinoma.