Extra-nodal Follicular Dendritic Cell Sarcoma

Fatima Obeidat, Maha Akkawi, Yousif Badran


Follicular dendritic cell (FDC) sarcoma, is a rare neoplasm, arising from the FDCs, accessory cells of the lymphoid system. About one third of cases occur in extra-nodal sites,, particularly the tonsils, spleen, gastrointestinal tract. Extra-nodal FDCS of the pharyngeal and parapharyngeal region is a very rare neoplasm that is often misdiagnosed as undifferentiated carcinoma or meningioma .
Microscopically, follicular dendritic cell tumors are composed of spindle cells with eosinophilic cytoplasm arranged in sheets, fascicles, and whorls, and storiform growth patterns, suggesting a diagnosis of sarcoma. The tumor cells are characteristically admixed with small lymphocytes, leading to an occasional misdiagnosis of lymphoma.
A 39 year old lady presented with 6 month history of headache. Head CT showed a right maxillary sinus mass extending to the nasal and orbital cavities and destructing the surrounding cranial bones including the skull base. The patient underwent endoscopic sinus mass biopsy.
Histologically, the mass was composed of spindle cells with bland looking nuclei arranged in a storiform pattern with focal necrosis and many mitotic figures. The differential diagnosis included sarcoma, lymphoma and poorly differentiated carcinoma.
Immunohistochemical stains showed strong immunoreactivity for CD21, CD23, and vimentin, focal positivity for SMA. The above findings support the diagnosis of extra-nodal follicular dendritic cell sarcoma.

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