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.

The cytology of extraskeletal Ewing sarcoma.

BACKGROUND: Extraskeletal Ewing sarcoma (EES) shares histologic, immunohistochemical, and molecular findings with ES of bone. The authors' goal in conducting this study was to examine the cytomorphologic features of EES. In addition, immunocytostaining for CD99/O13 was performed in all cases, and cytogenetic and molecular data were available in about half of the cases. METHODS: The authors studied 20 aspiration cases, all with histopathologic confirmation, and also conducted immunohistochemistry and/or molecular studies. RESULTS: All cases had cellular smears with many single cells and focal clustering. Numerous naked nuclei and focal crush artifacts were seen. Mitosis and necrosis were rare. Four cases had cytoplasmic vacuoles. Five cases showed nuclear molding. Seventeen cases (85%) exhibited small cells with scanty cytoplasm and nuclei with fine chromatin and small nucleoli, representing the so-called typical variant. One case (5%) revealed cells with abundant cytoplasm, large nuclei, and large eosinophilic nucleoli, an example of the atypical or large cell variant. Two cases (10%) had features in between, with cells showing a fair amount of cytoplasm and medium-sized nucleoli, representing the intermediate variant. Nuclear grooves, described as common in the latter, were rare. In all cases, in either cytologic or corresponding histologic material, CD99/O13 immunocytostaining showed strong membranous reactivity. In addition, cytogenetic and/or molecular evidence of ES specific chromosomal translocation was demonstrated in histologic or cytologic material in 10 cases. CONCLUSIONS: EES shows cytologic features similar to ES of bone, with a spectrum of changes ranging from the typical appearance in a majority of cases to intermediate and atypical variants in a minority of cases. CD99/O13 immunocytostaining and/or molecular studies, particularly in the intermediate and atypical variants, may help in establishing a definitive fine-needle aspiration diagnosis, thus avoiding an open surgical biopsy.