Medulloblastoma with focal divergent/teratoid differentiation.

Medulloblastomas with myogenic differentiation, previously termed medullomyoblastomas, form rare variants of medulloblastomas. Occasional tumors showing combined myogenic differentiation and melanotic tubular structures have also been described. On studying the records of a tertiary-care super specialty hospital, of 80 cases of medulloblastoma in a 5-year period, 36 showed nodular islands of neuronal, three myogenic, two glial, and one melanotic differentiation. Of the three cases of medulloblastomas with myogenic differentiation, we came across an extremely rare variant of medulloblastoma showing, in addition to the predominant primitive neuroectodermal component, a single minute nodular focus of 0.8 cm diameter, with divergent differentiation into mainly myogenic, epithelial, cartilaginous, and osseous lineages. Two ependymoblastic rosettes were also identified at different foci. In conclusion, a medulloblastoma with a small nodular island of divergent differentiation into various lineages has been seldom documented in literature. Microscopic foci of multilineage differentiation may be explained by the teratoid potential of medulloblastoma, or pluripotent nature of the neural crest cells, and requires extensive sampling for detection. It remains to be confirmed through more reports whether medulloblastomas with differentiation respond to a treatment protocol similar to that of medulloblastomas.