[Gliomedullomyoblastoma. A contribution to the morphology and biological behavior of myogenic brain tumors (author's transl)].

On the basis of an own observation and 38 cases found in the literature problems of histogenesis, classification and biological behavior of myogenic brain tumors and mixed neoplasms with myogenic elements are discussed. In a 2-year-old boy, 2 months after first clinical symptoms, a tumor of the walls of the 4th ventricle had been removed. The growth showed a large variety of histological structures. Irregularly arranged bundles of long muscle fibers with centrally located nuclei and cross striation were the most striking feature. Large cells with prominent nucleoli resembling ganglion cells were identified electronmicroscopically as rhabdomyblasts. Other areas were composed of astrocytic elements or of honeycomb-like structures usually observed in oligodendrogliomas. In serial sections small cells with dark nuclei typical for medulloblastomas were found in small areas. The body died 15 months after the onset of symptoms. The autopsy revealed a relapse in midline structures of the cerebellum. The histological picture differed substantially from that of the primary neoplasm. It was composed only of small cells, showed a large number of collagenous fibers and corresponded to a demoblastic medulloblastoma. The histological variety is regarded as an expression of the pluripotency of neoplastic elements, which are evidently capable to form neuroectodermal as well as mesenchymal structures. It is emphasized that an overgrowth more anaplastic cells led to the described morphological changes. Gliomedullomyoblastoma is regarded as a special variant of medulloblastoma with an unfavourable prognosis.