Medulloblastoma

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.

Location

Medulloblastoma occurs in the 4th ventricle of the brain and may invade the cerebellum —the lower, rear portion of the brain—or the dorsal brain stem. They may spread throughout the brain and spinal cord as well in the surrounding fluid.

Symptoms

The most common symptoms of medulloblastoma include changes in appetite and symptoms of increased pressure on the brain (e.g., headache, nausea, vomiting, and drowsiness, as well as problems with coordination). Unusual eye movements, fatigue, irritability, and behavioral changes may also occur.

Treatment

Treatment consists of surgical removal of as much tumor as possible followed by radiation and chemotherapy (in children ≥3-4 years of age at diagnosis). Radiation therapy is generally delayed in very young children due to the risks to the developing brain, so post-operative chemotherapy alone is utilized in children diagnosed with medulloblastoma as infants or toddlers. Many medulloblastoma patients may participate in clinical trials to get access to emerging therapies.

Prognosis

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:

Children (ages 0-14): 72.3%
Adolescents and Young Adults (ages 15-39): 78.5%
Adults (ages 40+): 66.2%

Incidence

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.

Age Distribution

Medulloblastoma occurs in people of all ages, most commonly among children 1-9 years of age at diagnosis

Risk Factors

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 Profile

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.

Additional Resources

Content last reviewed:

April 2022 by Holly B. Lindsay, MD, MS and Donald Williams (Will) Parsons, MD, PhD