Oncogene amplification is uncommon in cerebellar primitive neuroectodermal tumor (medulloblastoma) and its frequency and diversity are greater in medulloblastoma cell lines. We describe a medulloblastoma in a 10-year-old-girl with striking neuronal differentiation evident in the islands of ganglion cells intermixed with more primitive undifferentiated cells. The islands of ganglion cells showed prominent synaptophysin positivity. Karyotypic analysis revealed hypo- and hyperdiploidy with multiple random rearrangements and double minute chromosomes. Differential polymerase chain reaction and Southern blot analysis revealed up to 25-fold MYCN amplification.