Image Description
Numerous histologic subtypes of medulloblastoma have been described. Classic medulloblastoma (undifferentiated) consists of sheets of small round blue cells as shown in this image. Embryonal tumors comprise about 20% of pediatric brain tumors. Medulloblastoma is the most commonly seen member of this group. Others include atypical teratoid/rhabdoid tumor and the so-called primitive neuroectodermal tumor. Histologically, they all share the presence of primitive appearing small round blue cells with high N:C ratio, hyperchromatic nuclei and brisk mitotic activity.