[Granular cell tumor of a cerebral hemisphere: value of gliofibrillary protein acid assay].

A patient with a left parieto-occipital tumor presented generalized convulsions, and aphasia with alexia and agraphia. Diagnosis was confirmed by CT scan. Partial excision only was possible and was followed by radiotherapy. Histology showed the tumor to be composed of moderate and large sized cells with a granular PAS+ cytoplasm. Protoplasmic astrocytes were numerous at the periphery. Electron microscopy demonstrated typical features of Abrikossof's granular cell tumor: heterogeneous granulations constituted mainly of secondary lysosomes, autophagic vacuoles, multivesicular bodies, and rare angular bodies. The granular cells were interspersed with astrocytes, the feet of which were implanted on the capillary basal membrane. Immunoperoxidases assay of gliofibrillary protein acid demonstrated high levels in the intercellular prolongations, considered here to be astrocytic, but weak concentrations in the granular cells. This suggests uptake by the latter cells of adjacent astrocytic gliofibrillary protein acid, especially as the action of an anti-albumin serum on the tumor demonstrated that the granular cells can take up extracellular proteins by a passive mechanism. These findings stand against an astrocytic origin of the tumor. Comparison with other granular cell tumors, particularly pituicytomas, provides evidence of morphological unity, but cerebral granular cell tumors are rich in astrocytes, whereas these are absent in pituicytomas. The oncogenic unity of these tumors has not been established.