The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) has provided a set of uniform diagnostic terminology including benign (B), atypia of undetermined significance (AUS), follicular
neoplasm (FN), suspicious for
malignancy (SM),
malignancy (M), and nondiagnostic (ND) for the interpretation of thyroid fine-needle aspiration (FNA). We applied this terminology on our 1,382 thyroid aspirates in a community practice setting, which included 539 cases of B (39%), 376 cases of AUS (27.2%), 116 cases of FN (8.4%), 37 cases of malignant (2.7%), 36 cases of SM (2.6%), and 278 cases of ND (20.1%). Two hundred twenty-one cases (16%) of thyroid FNA had corresponding follow-up
thyroidectomies. Each diagnostic category represented a unique association with risk of
malignancy and risk of
neoplasm. Based on histologic follow-up, the risk of
neoplasm (including benign and
malignant neoplasm) was B 14%, AUS 44%, FN 67%, SM 77%, and M 100% and the risk of
malignancy was
B 3%, AUS 6%, FN 22%, SM 56%, and M 100%. The classification and follow-up recommendation of TBSRTC are appropriate for each category. Both B and AUS are low-risk lesions with low probability of
malignancy. FN predicts a higher rate for
neoplasm but an intermediate rate for
malignancy while SM carries a high risk for
malignancy.