The Bethesda System for Reporting Thyroid Cytopathology: A Single-Institution Retrospective Analysis of 2,479 Cases
Ashley S Inman, Michael Morton, Harvey M Cramer, Howard H Wu. Indiana University School of Medicine, Indianapolis, IN; Memorial Sloan Kettering Cancer Center, New York City, NY
Background: The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) provides a uniform diagnostic nomenclature and classification system, including 6 major categories - benign (B), atypia of undetermined significance (AUS), follicular neoplasm (FN), suspicious for malignancy (SM), malignancy (M) and non-diagnostic (ND), for the interpretation and reporting of thyroid fine-needle aspirates (FNA). We retrospectively applied the TBSRTC terminology to thyroid FNA cases previously diagnosed at our institution in order to assess the implied risks of malignancy for each of the 6 major diagnostic categories.
Design: A computer search of our anatomic pathology information system was performed for the 7-year period from 2003 to 2010 and all thyroid FNA cases were identified. Five cases of parathyroid hyperplasia were excluded from this analysis. The FNA diagnoses were reclassified according to TBSRTC and correlated with the available follow-up thyroid surgical pathology reports. The risk of malignancy (malignant tumors excluding papillary microcarcinoma) and the risk of neoplasm (malignant tumors including papillary microcarcinoma plus adenomas) were calculated for each diagnostic category.
Results: A total of 2,479 thyroid FNA aspirates were performed during the 7-year period encompassed by this study. The cytologic diagnoses were as follows: 1,751 cases (71%) were B, 311 cases (13%) were AUS, 72 cases (3%) were FN, 58 cases (2%) were SM, 181 cases (7%) were M, and 101 cases (5%) were ND. Surgical pathology follow-up was obtained in 348 cases (14%). For the subset of cases with surgical pathology follow-up, the risk of a neoplasm for each diagnostic category was as follows: B 40%, AUS 71%, FN 89%, SM 88%, and M 99%. The risk of malignancy for each category was B 4%, AUS 15%, FN 24%, SM 88%, and M 99%.
Conclusions: The TBSRTC classification system stratifies the risk of thyroid neoplasia and malignancy in a manner that is simple, understandable and useful for therapeutic decision-making. Follow-up recommendations are appropriate given the significant differences in the risk of neoplasia and malignancy associated with each of the TBSRTC diagnostic categories.
Wednesday, March 21, 2012 1:00 PM
Poster Session VI # 71, Wednesday Afternoon