35. Follicular dendritic cell sarcoma of the nasopharynx

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Background: Follicular dendritic cell sarcoma (FDCS) is a rare low-grade sarcoma, which presents as intranodal or, more commonly, extranodal disease at a wide variety of sites. To date, only eight cases of FDCS of the nasopharynx are reported.1,2 The morphological spectrum includes fascicular, whorled and sheet-like architecture with bland spindled to ovoid cells and possible nuclear pseudoinclusions. Occasionally, high-grade features including cytological atypia, numerous mitoses and necrosis are seen. Aims: To present the case of a 24-year-old female with a nasopharyngeal mass, subsequently diagnosed as FDCS. Methods: A biopsy was obtained which showed sheets of malignant cells, admixed with lymphocytes and occasional neutrophils. The cells had pale fibrillary cytoplasm, appearing syncytial in some areas. The nuclei were ovoid with fine chromatin, although with significant anisonucleosis, frequent large nuclear pseudoinclusions and occasional nucleoli. Numerous mitoses and areas of necrosis were present. Despite this unusual morphology, immunohistochemistry was positive for CD21, CD23 and CD35, indicative of FDCS. Results and conclusions: FDCS is an uncommon entity which, combined with variant morphology and an unusual site, can lead to a high risk of misdiagnosis; reported in four of six nasopharyngeal cases (67%).2 A high index of suspicion and broad immunohistochemical panel are required for diagnosis, particularly when high-grade features are present.