Abstract

Soft tissue perineurioma is a very rare tumor composed of entirely of neoplastic perineurial cells. A 54-year-old woman presented with a palpable mass in the right lower leg. The mass was excised. Grossly, the tumor measured 2.0x2.0x1.5 cm. The cut surface was well circumscribed, pale pinkish gray, and rubbery soft. Histological examination showed that the tumor was composed of spindle cells within collagenous and myxoid stroma. The tumor cells had elongated, tapering nuclei with long and thin cytoplasmic processes, and were arranged in fascicular, whorled, and storiform pattern. The tumor cells were positive for epithelial membrane antigen and collagen type IV and negative for S-100 protein. Ultrastructurally, tumor cells showed long and thin cytoplasmic processes, pinocytic vesicles, and incomplete external lamina. The diagnosis of soft tissue perineurioma was confirmed by immunohistochemical stain and ultrastructural study.

• Keywords: Perineurioma;Immunohistochemistry;Ultrastructure