Evaluation of thyroid nodules classified as Bethesda category III on cytology and their malignancy rate: An institutional experience

BACKGROUND: Thyroid gland nodules are common and fine-needle aspiration (FNA) is the gold standard for screening those nodules. The Bethesda system for reporting thyroid cytolopathology standardized reporting thyroid nodules aspirations, but atypia of undetermined significance or follicular lesion of undetermined significance (Bethesda category III) was the most controversial category. The aim of our study is to review our institutional experience and analyze the clinical implications of making a diagnosis of AUS/FLUS (Bethesda category III). METHODS: This is a retrospective study of an 889 thyroid FNAs from 825 patients in Salmaniya Medical Complex, during (January 2013–December 2017). RESULTS: The most common cause for designating cases as AUS/FLUS (Bethesda category III) was the presence of features suggestive of papillary thyroid carcinoma, but not quite fulfilling the criteria for such diagnosis. Ninety-six cases were diagnosed as AUS/FLUS (10.7%), in which 26 (27%) patients underwent surgery without repeating the FNA, 25 (26%) underwent a second FNA and 43 (44.7%) patients were followed up by ultrasound. On repeating the FNA, 1 (4%) was unsatisfactory, 13 (52%) were benign, 10 (40%) were AUS/FLUS, and only 1 (4%) was categorized as malignant. Thirty cases were surgically excised, in which 4 (13.3%) were diagnosed as follicular adenoma, 2 (6.6%) as Hurthle cell adenoma, 9 (30%) as multinodular goiter, 5 (16.6%) as multinodular goiter with Hashimoto thyroiditis, 1 (3.3%) as colloid nodule with Hashimoto thyroiditis, and 9 (30%) as papillary thyroid carcinoma. Among all the cases diagnosed initially as AUS/FLUS (Bethesda category III), 9 (9.3%) cases were diagnosed as papillary thyroid carcinoma. CONCLUSION: Diagnostically, we almost meet the international standards of designating cases with AUS/FLUS (Bethesda category III) and approximate the risk of malignancy. However, the clinical management's guidelines should be followed to decrease the risk of unnecessary surgeries and their complications. There is a statistically significant correlation between the age and gender with the final histopathology report, respectively.