Medulloblastoma

Medulloblastomas have the typical appearance of a small round blue cell tumor. This family of tumors includes atypical teratoid/rhabdoid tumor as well as the so-called primitive neuroectodermal tumor. Cytogenetics: The most common cytogenetic abnormality seen in medulloblastomas is loss of chromosome 17p, usually resulting from the formation of isochromosome 17q along with duplication of the long arm (seen in about 30% of cases).