Malignant peripheral nerve tumors: a clinicopathological and electron microscopic study.

Sixteen cases of malignant peripheral nerve tumors that were recorded in the files of the Department of Orthopedics, National Cancer Center Hospital, Tokyo, between 1972-July 1983 were studied clinicopathologically. The patients' ages ranged from 24-51 years, and both sexes were affected equally. Histologically, in 13 cases of nerve sheath tumors the tumors were spindle-cell type, two of these patients had manifestation of multiple neurofibromatosis (von Recklinghausen's disease). One malignant epithelioid schwannoma was found to arise from the tibial nerve. Other two cases were of primitive neuroectodermal tumors (primary malignant peripheral neuroblastoma) which showed rosette formation. The common primary symptoms in all patients were a noticeable mass which increased in size over a variable period of time, with or without associated pain and tenderness. Ultrastructural findings of spindle-cell type (in 7 tumors examined) and epithelioid type (1 tumor) showed evidence of Schwann cell differentiation of the tumors in all cases. Immunohistochemically, by the PAP method (Sternberger), staining for S-100 protein was positive in 3 of 14 tumors. Ultrastructural findings in two S-100 protein-positive cases showed evidence of Schwann cell differentiation better than the S-100 protein-negative cases, such as pronounced interdigitation of cytoplasmic processes, presence of fibrous long-spacing collagen and well-developed basal lamina. Local recurrence occurred in nine patients, and metastasis was found in five. The total 5-year survival rate was 58.5%. Tumors associated with multiple neurofibromatosis and primary peripheral neuroblastomas had the worst prognosis. Complete removal of the tumor by means of wide excision as primary treatment seemed to be the most important factor in decreasing the morbidity and mortality rates.