Follicular dendritic cell tumor of the parapharyngeal region

Follicular dendritic cell (FDC) tumors are rare. A majority of the reported cases were confined to the lymph nodes. We report a case of FDC tumor occurring in the parapharyngeal region in a 45-year-old woman.

Characteristic histopathologic features of the excised primary and recurrent parapharyngeal tumors in conjunction with immunohistochemistry and electron microscopy helped us to arrive at a diagnosis of FDC tumor.

Histopathology of primary excision revealed a lobulated tumor with a suggestion of ill-defined whorls. The most striking feature was regular occurrence of aggregates of lymphocytes within the tumor, especially around the blood vessels. The anatomic location together with the histology indicated the possibilities of either a meningioma, a salivary gland tumor, or a nerve sheath tumor. Immunostains for cytokeratin (CK), S-100 protein, and smooth muscle actin (SMA) were negative. However, the tumor cells showed strong immunoreactivity for epithelial membrane antigen (EMA) and vimentin. A diagnosis of parapharyngeal meningioma appeared to be the closest possibility. One year later, the patient developed a recurrence at the same site. A reexcision showed an identical tumor with an additional feature of lymphatic embolization and angioinvasion. A review of the entire case with further immunoreactivity for CD21 and CD35 confirmed the diagnosis of FDC.

Follicular dendritic cell tumor has distinctive morphologic features and immunohistochemical profile. It is also characterized by considerable potential for recurrences.