Medullomyoblastoma: case report.

This 7-year-old boy presented with a 2-week history of headache, nausea, vomiting, anorexia, lethargy, and unsteadiness of gait. Brain magnetic resonance imaging (MRI) revealed a cystic mass within the vermis of the cerebellum. A suboccipital craniectomy was performed to remove a tumor that contained primitive neuroectodermal cells with florid skeletal muscle differentiation. Immunohistochemical studies and electron microscopy confirmed the presence of both a primitive neuroectodermal component and rhabdomyoblastic differentiation, consistent with the diagnosis of medullomyoblastoma. This exceedingly rare tumor of the cerebellar vermis of children is characterized by two components: primitive neuroectodermal tumor cells and skeletal muscle. Although the histogenesis remains uncertain, advances in immunohistochemistry and electron microscopy suggest the origin of this tumor from a multipotential stem cell precursor.