Medulloblastoma is the most common malignant (cancerous) central nervous system tumor of childhood. It is a fast-growing, high-grade tumor that may spread throughout the central nervous system. Medulloblastoma can be classified into 4 subgroups and 12 subtypes based on genetic and molecular profiling, each with distinct clinical features and outcomes.
Prognosis means a prediction of outcome. This information is usually based on information gathered from groups of people with the same disease. It is important to remember these statistics are not individualized.
The 5-year relative survival rates for medulloblastoma by age group are as follows:
Medulloblastoma tumors commonly occur in infants and children. They account for about 1,500 cases in infants and children per year in the United States, which is about 10% of all tumors diagnosed in infants and children.
Medulloblastoma is much less common in adults.
Like many tumor types, the exact cause of medulloblastoma is not known. However, up to 5% of patients with medulloblastomas have an underlying inherited cancer predisposition syndrome such as Li-Fraumeni syndrome, Gorlin syndrome, or familial adenomatous polyposis.
Molecular profiling is the detection of specific genes, proteins, or other molecules in a tumor. This information helps confirm tumor diagnosis, inform treatment options, and predict prognosis.
Medulloblastoma can be classified into 4 molecular subgroups: WNT, SHH, group 3, and group 4, all of which have characteristic genetic and clinical features and prognoses. These subgroups can further be divided into 12 subtypes: 2 WNT, 4 SHH, 3 group 3, and 3 group 4.
In patients ≥3 years of age at diagnosis, high-risk features (suggesting a worse clinical outcome) include metastatic disease and residual tumor following resection. In patients with the SHH subtype, high-risk molecular features include a p53 mutation, N-MYC or GLI2 amplification, or chromosome 14q loss or deletion in the tumor. In patients with group 3 medulloblastoma subtype, high-risk molecular features include MYC amplification or isochromosome 17 in the tumor. In patients with group 4 medulloblastoma, the high-risk molecular feature is the presence of chromosome 11.
April 2022 by Holly B. Lindsay, MD, MS and Donald Williams (Will) Parsons, MD, PhD
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