Classic medulloblastoma

Classic medulloblastoma (Orphanet code 251867) is a malignant embryonal tumor of the cerebellum, the part of the brain located in the posterior fossa that controls balance, coordination, and motor function. It is classified under ICD-10 code C71.6 (malignant neoplasm of the cerebellum). Medulloblastoma is the most common malignant brain tumor in children, and the classic histological variant is the most frequently encountered subtype, characterized by densely packed small round blue cells with high nuclear-to-cytoplasmic ratios arranged in sheets. Classic medulloblastoma is distinguished from other histological variants such as desmoplastic/nodular, extensive nodularity, and large cell/anaplastic types. The tumor primarily affects the central nervous system, arising in the cerebellum and frequently obstructing the flow of cerebrospinal fluid, leading to hydrocephalus. Key symptoms include headaches (often worse in the morning), nausea and vomiting, ataxia (unsteady gait and poor coordination), visual disturbances including papilledema, and signs of increased intracranial pressure. Because medulloblastoma has a propensity to disseminate through the cerebrospinal fluid, metastatic spread along the spinal cord (leptomeningeal dissemination) can occur, potentially causing back pain or neurological deficits in the limbs. Treatment for classic medulloblastoma typically involves a multimodal approach. Surgical resection of the tumor is the first step, aiming for maximal safe removal. This is followed by craniospinal irradiation (radiation therapy to the entire brain and spinal cord) in children over approximately three years of age, and adjuvant chemotherapy. Risk stratification into standard-risk and high-risk groups guides treatment intensity. Standard-risk patients (those with near-total resection and no metastatic disease) generally have a favorable prognosis, with five-year survival rates exceeding 70-80%. Molecular subgrouping (WNT, SHH, Group 3, Group 4) has become increasingly important in refining prognosis and guiding therapy, with WNT-subgroup classic medulloblastomas carrying a particularly favorable outcome. Ongoing clinical trials are investigating de-escalation strategies for low-risk patients and intensified or targeted therapies for high-risk groups.

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