Background Follicular dendritic cell (FDC) tumors are rare. A majority of t
he reported cases were confined to the lymph nodes. We report a case of FDC
tumor occurring in the parapharyngeal region in a 46-year-old woman.
Methods. Characteristic histopathologic features of the excised primary and
recurrent parapharyngeal tumors in conjunction with immunohistochemistry a
nd electron microscopy helped us to arrive at a diagnosis of FDC tumor.
Results. 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 indic
ated 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 st
rong immunoreactivity for epithelial membrane antigen (EMA) and vimentin. A
diagnosis of parapharyngeal meningioma appeared to be the closest possibil
ity. One year later, the patient developed a recurrence at the same site. A
reexcision showed an identical tumor with an additional feature of lymphat
ic embolization and angioinvasion. A review of the entire case with further
immunoreactivity for CD21 and CD35 confirmed the diagnosis of FDC.
Conclusions. Follicular dendritic cell tumor has distinctive morphologic fe
atures and immunohistochemical profile. It is also characterized by conside
rable potential for recurrences. (C) 1999 John Wiley & Sons, Inc.