Granular cell tumour of the brain and its cellular identity.

Two cases of cerebral granular cell tumour are reported. In Case 1 the tumour arose from the genu of the corpus callosum, and in Case 2 it was found in the frontotemporoparietal lobes. Biopsy and autopsy specimens were examined with light and electron microscopy, and histochemical characteristics of the granule were analysed. Tumour cells from these two cases showed pleomorphism, but abundant granules in the cytoplasm were the most characteristic feature in these tumours. The granules were not stained by Sudan III and Sudan black, but were eosinophilic. They were PAS positive and not digested by diastase. Okamoto's reaction for glycolipid was positive after treatment by pyridine. They were also positive in Hotchkiss' method for glycolipid modified by Morrison and Hack, following immersion in chloroform and methanol solution. Histochemically, it was thought that granules consisted of glycoprotein. In the electron microscopic study dense bodies, multivesicular bodies, and vacoules were seen in tumour cells, especially in the neoplastic granular cells. It was assumed that the tumour cells originated from astrocytes, because of the cytoplasmic processes of the tumour cells were stained blue with PTAH, and contained microfibres of 80 A width. Gemistocytic astrocytes seen in the periphery of the tumour were also evidence indicating the neoplastic cell origin.