Medulloblastoma, classified as an embryonal tumor, is a common malignant tumor in children, accounting for 15%–20% of pediatric intracranial tumors. It predominantly occurs before the age of 10, with a male-to-female incidence ratio of 2:1. The tumor most frequently originates in the cerebellar vermis, located at the roof of the fourth ventricle, and is prone to causing obstructive hydrocephalus. Metastases outside the skull, including to bones, lymph nodes, and lungs, occur in 5% of cases. Clinically, increased intracranial pressure and ataxia are the primary manifestations.
Imaging studies, such as CT and MRI, typically show a midline solid tumor in the posterior fossa. On T2-weighted MRI, the tumor usually presents as a slightly hyperintense signal, with significant enhancement after contrast administration. Surgical resection of the tumor is performed as completely as possible, followed by adjuvant radiotherapy and chemotherapy.
Based on molecular and genetic characteristics, medulloblastomas are classified into four subtypes: WNT-activated, SHH-activated, and numerically labeled Group 3 and Group 4. Prognosis varies across these subtypes, with WNT-activated tumors having the most favorable outcomes and Group 3 tumors the poorest prognosis.