Glioblastoma multiforme occurring 13 years after treatment of a medulloblastoma.

Although medulloblastoma is said to be capable of astrocytic differentiation, the development of an astrocytic neoplasm in association with a medulloblastoma is extremely rare. We report the light and electron microscopic features of a supratentorial glioblastoma that occurred 13 years after radiation therapy for a cerebellar medulloblastoma. The diverse ultrastructural features of the glioblastoma may reflect the multipotentiality of the cells in medulloblastoma. An alternate interpretation is that the glioblastoma represents a radiation-induced neoplasm after therapy for a medulloblastoma.