What is medulloblastoma?

➢ Usually presents as an irregular posterior fossa mass arising near the midline of the cerebellum ➢ May extend into the fourth ventricle above the brain stem. ➢It is one of the small round blue cell tumors that most often occur in children. ➢These highly malignant, poorly differentiated tumors commonly spread into the subarachnoid space and seed by the CSF into the spinal canal. ➢Those associated with mutations in the WNT signaling pathway have the best prognosis. ➢ Medulloblastomas are of neuroectodermal origin and occur in the cerebellar vermis in children, where they can occlude the fourth ventricle to cause hydrocephalus. ➢ In older patients, these tumors more commonly arise within the cerebellar hemispheres. ➢These primitive tumors are very radiosensitive. ➢About a third of medulloblastomas occur in patients 15 to 35 years old. ➢Two thirds are found in patients younger than 15 years