Spinal malignant nerve-sheath tumor or cellular schwannoma? A striking difference in prognosis.

Cellular schwannoma, a recently delineated entity, has a histological appearance mimicking that of malignant neoplasms. The aim of this study was to determine the outcome for patients treated for a spinal cellular schwannoma or malignant nerve-sheath tumor. A histological re-examination was conducted of 283 spinal tumors, considered to originate from a nerve root, that were treated in the Department of Neurosurgery between 1953 and 1985. After re-examination, 50 of these were determined to be other tumors or non-neoplastic lesions. The review yielded eight cellular schwannomas and six malignant nerve-sheath tumors out of 233 of nerve-sheath origin. Immunohistochemical staining with a commercially available polyclonal antibody against S-100 protein was positive in all cases of cellular schwannoma, but negative for the malignant tumors. Clinical outcome was favorable for patients with cellular schwannomas, but uniformly poor for those with the malignant tumors.