A Case of Perineurioma

Abstract

Perineurial cells, which normally surround the nerve fascicles within a nerve, can be distinguished from Schwann cells by their immunoreactivity for epithelial membrane antigen and lack of reactivity for S-100 protein. Perineuriomas are uncommon, slowly growing, usually benign tumors composed of well-differentiated perineural cells. We experienced a case of perineurioma in a 44-year-old man. This tumor was a 2 cm sized subcutaneous non-tender movable mass on the left posterior popliteal area. Histologically, the tumor was a circumscribed but non-encapsulated lesion and composed of spindle cells with elongated bipolar cytoplasmic processes, fusiform nuclei, and well-defined palely eosinophilic cytoplasm. Immunohistochemically, most of the tumour cells stained positive with epithelial membrane antigen and vimentin, but failed to stain with S-100 protein, neurofilament, CD34, cytokeratin, chromogranin A, synaptophysin, and Bodian stain.