Cerebellar neoplasm of mixed mesenchymal and neuroepithelial origin. Case report.

A 3 1/2-year-old boy had a neoplasm of mixed mesenchymal and neuroepithelial origin in the cerebellar vermis. The tumor was composed of rhabdomyosarcoma and medulloblastoma. There was additional differentiation within the neuroepithelium, including neoplastic neurons, neuroblasts, astroglia, oligodendroglia, ependymal cells as well as foci of glioblastomatous transformation. It is suggested that this combined tumor arose from the neural crest or combined neural crest and neural tube. The rhabdomyosarcoma could have arisen from the mesenchymal portion of the neural crest, and the medulloblastoma from the neuroectodermal part of the neural crest or from the neural tube itself. The two tumor types formed a neoplasm of mixed mesenchymal and neuroepithelial origin.