Cerebral granular cell tumor: immunohistochemical and electron microscopic study.

A rare intracerebral granular cell tumor (GCT) was studied by immunocytochemical and ultrastructural methods. The tumor was composed of two cell types--filament-rich and granular cells. Granular cells contained PAS-positive, diastase-resistant granules that ultrastructurally corresponded to autophagic cytosegresomes. Glial fibrillary acidic protein, the intermediate filament protein specific for astrocytes, was demonstrated in the filament-rich and, to a lesser extent, in the granular cells. Unlike noncerebral GCT, neither S-100 protein nor vimentin was detected in the tumor cells. On the other hand, both cerebral and noncerebral GCT were labeled immunocytochemically with peanut lectin (Arachis hypogaea). The results suggest that cerebral GCT share some features with noncerebral GCT, but differ in other respects. They further suggest that GCT may be derived from different cell types depending on the tissue of origin, and that cerebral GCT may be derived from astrocytes.