Fine-needle aspiration of a follicular dendritic-cell tumor: report of a case and review of the literature.

Follicular dendritic-cell tumors (FDCT) are rare neoplasms, well-characterized in surgical pathology material. There are, however, few cytopathology reports. We describe the fine-needle aspiration (FNA) findings of a histologically confirmed FDCT. Conventional smears and a cell block showed large spindle to oval neoplastic cells admixed with small mature lymphocytes. The neoplastic cells were present mainly in small syncytial clusters. Immunostains for CD21 and CD35, performed on the cell block, were positive in the neoplastic cells. The diagnosis was fully confirmed by the presence of typical immunohistochemical and ultrastructural features on the surgically removed tumor. The differential diagnosis of FDCT is broad and includes other tumors characterized by an admixture of large neoplastic cells and small mature lymphocytes, such as thymomas, lymphoepithelioma-like carcinomas, and interdigitating dendritic-cell tumors. It may not be possible to diagnose FDCT based on FNA material without the use of immunocytochemical and electron microscopic studies. Certain cytomorphological characteristics, however, might suggest its diagnosis and allow the practicing cytopathologist to perform confirmatory studies.