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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