Malignant granular cell tumor of the right sciatic nerve. Report of an autopsy case with electron microscopic, immunohistochemical, and enzyme histochemical studies

An autopsy case of a malignant granular cell tumor of the right sciatic nerve was reported. The surgically excised malignant granular cell tumor of a 43-year-old woman showed a close relationship with the sciatic nerve, and postmortem examination disclosed extensive metastases. Electron microscopic observations of the material obtained at surgery revealed many diagnostic granules containing myelin figures, as well as basement membrane-like structures around some of the tumor cells. Electron microscopic acid phosphatase staining suggested that the granules could be of a lysosomal origin. Immunohistochemical investigation showed the presence of S-100 protein in the tumor cells, a finding which is believed to be specific for the nervous system. And, focally, the cytoplasmic processes accompanied by basement membrane mimicked Schwann cells. This evidence suggested the highly malignant nature of the malignant granular cell tumor of probable Schwann cell origin.