Peripheral nerve sheath tumors of the head and neck.

The head and neck region is a common location for benign peripheral nerve sheath tumors (PNST) and a rare site for malignant PNST. The diagnostic distinction between schwannoma (neurilemmoma) and benign neurofibroma remains clinically and prognostically important. Most benign PNST are schwannomas, and these do not have a recognized malignant potential. Malignant PNST arise de novo or from benign neurofibromas. The definitive diagnosis of malignant PNST may be difficult or impossible using only routine light microscopy. Electron microscopy and immunohistochemistry are special techniques that may be helpful. The prognosis in patients with malignant PNST depends heavily on the extent of surgical excision, size of the primary tumor, and presence or absence of von Recklinghausen's neurofibromatosis.