Should "Indeterminate" Diagnoses Be Used for Thyroid Fine-Needle Aspirates of Nodules Smaller Than 1 cm?

Context.-The Bethesda System for thyroid fine-needle aspirates does not account for the size of the lesion that is aspirated. Objective.-To determine whether the size of the lesion would be helpful in order to reduce indeterminate thyroid aspirations. Design.-We correlated the results of all thyroid aspirations and surgical resection for the last 16 years at our institutions. Results.-A total of 9080 cases were aspirated and 1393 resections were performed. Of those resected, a total of 236 (17%) were classified as atypical follicular cells of undetermined significance, and 256 (18%) were classified as suspicious for a follicular/Hurthle cell neoplasm. A total of 52 incidental papillary carcinomas were identified in these indeterminate cases at resection (52 of 492; 11%). Thirty-seven (16%) atypical follicular cells of undetermined significance cases and 21 (8%) suspicious for a follicular/Hurthle cell neoplasm cases were for nodules smaller than 1 cm in diameter. When cases subtyped as atypical, a papillary carcinoma cannot be ruled out, were removed (13 cases), the remaining 24 and 21 aspirates identified 3 tumors each (13% and 14%), all papillary carcinomas. Together, the incidence of identified carcinomas was not significantly different than that of incidental carcinomas (13% versus 11%, P = .48). The rate of identified carcinomas was significantly less than for similar indeterminate cases smaller than 1 cm (excluding cases of atypical, papillary carcinoma cannot be ruled out) (88 of 330 cases; 27%; P = .05). Conclusions.-For nodules smaller than 1 cm in our series, indeterminate aspirates without features of papillary carcinomas have the same risk of malignancy as benign aspirates.