Medulloblastoma of brain

**Definition:** A malignant, invasive embryonal neoplasm arising from the cerebellum. It occurs predominantly in children and has the tendency to metastasize via the cerebrospinal fluid pathways. Signs and symptoms include truncal ataxia, disturbed gait, lethargy, headache, and vomiting. There are four histologic variants: anaplastic medulloblastoma, desmoplastic/nodular medulloblastoma, large cell medulloblastoma, and medulloblastoma with extensive nodularity.

**Long definition:** Medulloblastoma is the most common malignant brain tumour occurring in children, adolescents and young adults. It derives from the neuroectoderm and develops in the cerebellum (80% occur in the vermis and 20% occur in the hemispheres). It accounts for 10 to 20% of brain tumours and for 30% of tumours located in the posterior fossa.