Computed tomography of extracranial nerve sheath tumors with pathological correlation.

Computed tomography was obtained in 15 patients with extracranial nerve sheath tumors, including eight with neurofibromatosis. The studies included two schwannomas, six neurofibromas, four plexiform neurofibromas, and three neurofibrosarcomas. Lesions with attenuation values exceeding 30 Hounsfield units had dense bands of collagen in resected specimens. Eleven of the lesions had attenuation values which were significantly lower than muscle. Histological examination of hypodense lesions revealed five factors contributing to reduced attenuation values: (a) a population of lipid-rich Schwann cells; (b) the presence of adipocytes (transformed fibroblasts) in neurofibromas; (c) entrapment of perineural adipose tissue by plexiform neurofibromas; (d) a coalescence of interstitial fluid to form cystic spaces in schwannoma with Antoni B tissue; and (e) cystic degeneration secondary to infarction or necrosis within neurofibromas and neurofibrosarcomas.