Abstract
A case of cerebellar medulloblastoma with transitional features towards malignant fibrillary astrocytoma is described. In the cerebellum the tumour is characterised by extensive subpial infiltration with cells of undifferentiated type, and the astrocytic component could only be identified by a positive glial fibrillary acidic protein reaction. In the brainstem the character of the growth transforms to that of diffuse astrocytoma. This demonstrates the potential for differentiation existing in a "primitive" neuroepithelial neoplasm.