THYMIC EPITHELIAL-CELLS AS A DIAGNOSTIC PITFALL IN THE FINE-NEEDLE ASPIRATION DIAGNOSIS OF PRIMARY MEDIASTINAL LYMPHOMA

The cytologic diagnosis of primary mediastinal lesions is challenging due to the large number of lesions which may arise (i.e., lymphoma, th ymoma, germ cell tumor), often with overlapping cytomorphologic featur es. We present an instructive case of primary mediastinal non-Hodgkin' s large-cell lymphoma with sclerosis, entrapping thymic epithelium. Pr eoperative fine-needle aspiration yielded predominantly epithelial fra gments and few lymphoid cells, leading to the cytologic misdiagnosis o f thymoma. The entity of primary mediastinal large-cell lymphoma (LCL) is discussed and correlated with the cytologic features seen. In addi tion, histologic sections from 15 additional cases of primary mediasti nal LCL were evaluated to determine the frequency with which significa nt numbers of epithelial fragments may be observed. (C) 1997 Wiley-Lis s, Inc.