[409] Thymic Neoplasms: A Study of 59 Cases Diagnosed by Fine Needle Aspiration of the Anterior Mediastinum

Megan Redelman, Shaoxiong Chen, Harvey Cramer, Robert Emerson, Xiaoyan Wang. Indiana University School of Medicine, Indianapolis, IN

Background: Image-guided fine needle aspiration (FNA) has been used routinely for diagnosing anterior mediastinal lesions. In this study, we retrospectively reviewed 59 cases of thymic neoplasms diagnosed by FNA over a 20-year period and determined the accuracy and clinical utility of this diagnostic technique.
Design: A computerized search of our cytology database was performed for the 20-year period from 1990 through 2010 and all FNAs of the anterior mediastinum diagnosed as thymic neoplasms were identified. All cytology and correlating surgical reports as well as the clinical histories were reviewed and slides from selected cases were re-examined. Nondiagnostic FNA cases without correlating histology were not included in this study.
Results: A total of 59 cases of thymic neoplasm diagnosed by FNA were retrieved and histologic correlation was available for 43 (73%) cases. The FNA diagnoses were classified as: positive in 51 (87%), atypical/hypocellular in 6 (10%) and nondiagnostic in 2 (3%). Fifty-one positive cases included 27 thymomas (53%) and 24 thymic carcinomas (47%). The FNA diagnoses for the 35 of 51 cases (69%) that had histologic confirmation included 18 thymomas (51%) and 14 thymic carcinomas (40%). One case of large cell lymphoma (3%) was misdiagnosed as a malignant thymoma by FNA. For 2 poorly differentiated carcinoma cases (6%), histopathologic confirmation was not obtained due to surgical pathology sampling error. The histologic diagnosis for 6 FNA cases diagnosed as atypical/hypocellular included 1 thymoma, 1 thymic carcinoma, 1 undifferentiated malignant neoplasm, and 1 lymphoma. Two cases with follow-up surgical core biopsies remained inconclusive due to inadequate sampling. In addition, 1 thymoma and 1 thymolipoma were identified on the histologic follow-up of 2 nondiagnostic FNA cases.
Conclusions: FNA is a safe and valuable method for diagnosing thymic neoplasms. In this study, the overall diagnostic accuracy for the FNA diagnosis of thymic neoplasm was high and the misclassification rate was low (3%). When coupled with clinical and imaging findings, FNA should be considered as the biopsy method of first choice for the diagnosis of thymic neoplasms.
Category: Cytopathology

Tuesday, March 5, 2013 1:00 PM

Poster Session IV # 83, Tuesday Afternoon

 

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