Medulloblastoma with extensive nodularity (SHH medulloblastoma).

Medulloblastoma is the most common CNS embryonal tumor and the most common malignant tumor of childhood. Its overall incidence is 1.8 cases per 1 million people, with a childhood incidence of 6 cases per 1 million. 77 percent of patients are less than 19 years old. Medulloblastoma occurs in the 4th ventricle and usually presents with symptoms of increased intracranial pressure (headaches, nausea, vomiting) and signs of obstructive hydrocephalus. Medulloblastoma is both histologically and genetically defined with prognosis that depends on classification.