Large cell anaplastic medulloblastoma is a highly aggressive variant that represents about 25% of medulloblastomas. It is seen in young patients (age range at presentation 1 yr. to 4 yrs.) with a male predominance. It shows early tendency to disseminate via cerebrospinal fluid despite aggressive efforts at management with chemotherapy and radiation. The tumor is composed of large, anaplastic cells with vesicular nuclei that may display molding (as seen in this example), prominent nucleoli, and brisk mitotic activity. Areas of geographic necrosis and numerous apoptotic cells are a frequent finding.