Differentiation of Medulloblastoma. Studies including immunohistochemical localization of glial fibrillary acidic protein.

A series of medulloblastomas was studied by light microscopy. The tumors were variable; astrocytic, ependymal, neuronal, and probable oligodendroglial differentiation was present. Features of glioblastoma multiforme occurred in one case. Immunoperoxidase staining for glial fibrillary acidic protein (GFAP), an antigen found only in astrocytes and ependymal cells, revealed astrocytic differentiation in 11 of 13 cases. The two GFAP-negative tumors were histologically undifferentiated. A new classification of medulloblastomas is presented, based on the multiple types of differentiation of these tumors. Neuronal, astrocytic, ependymal, and small-cell types are described. Undifferentiated tumors were more frequent in younger children. The differentiation of medulloblastoma is correlated with recent experimental studies of gliogenesis and neurogenesis. A hypothesis that medulloblastoma is a stem-cell neoplasm is presented, based on these comparative data.