Intraneural malignant perineurioma: a case report and review of literature.

The great majority of malignant peripheral nerve sheath tumors (MPNSTs) exhibit Schwann differentiation. Few MPNSTs with perineurial differentiation are also named malignant perineuriomas. Benign perineurioms were classified as intraneural, extraneural (soft tissue), sclerosing, and reticular variant. Histopathological features of intraneural perineurioma are individual nerve axons surrounded by whorls of spindle-shaped cells arranged in an onion bulb-like pattern. However, intraneural malignant perineurioma is uncommon, its characteristic histological features were not clearly described yet. Positive for epithelial membrane antigen (EMA), glut-1 and claudin-1, is characteristic of malignant perineurioma. Herein, we report an intraneural malignant perineurioma in median nerve of a 13-year-old girl. The clinicopathological features were summarized and the related literatures were reviewed.