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What is medulloblastoma?

Medulloblastoma is a brain tumor of the cerebellum. The cerebellum controls balance and coordinated movements. The cerebellum is found near the brainstem in a region called the posterior fossa at the back of the brain.

This fast-growing tumor can spread to other areas of the brain and spinal cord through cerebrospinal fluid (CSF).

Graphic showing medulloblastoma in brain

The four colored areas of this tumor represent the four different molecular groups.


How common is medulloblastoma?

  • Medulloblastoma is the most common malignant brain tumor of childhood. It accounts for about 20% of all childhood brain tumors.
  • About 500 new cases are diagnosed in children in the United States each year.
  • Medulloblastoma occurs mainly in children but can be found in infants and adults. The most common age of diagnosis is between 5 and 9 years old
  •  Medulloblastoma is slightly more common in boys than in girls.

What are the symptoms of medulloblastoma?

Symptoms of medulloblastoma depend on several things, including the tumor’s size and location, the child’s age, and stage of development. Symptoms may include:

  • Headaches
  • Nausea and vomiting
  • Feeling tired or having changes in activity level
  • Clumsiness or loss of balance
  • Dizziness
  • Problems with handwriting
  • Change in vision

If the tumor has spread to the spinal cord, symptoms may include:

  • Back pain
  • Trouble walking
  • Problems controlling bladder and bowel functions

How are medulloblastomas classified?

Microscopic features of tumor cells, such as size and shape, are used to classify these tumors.

  • Classic medulloblastoma is made up of small, round cells. The cells are close together. A medulloblastoma cell has a dark nucleus. A nucleus is where the cell’s chromosomes, or DNA, is stored.
  • Desmoplastic or nodular medulloblastoma looks like round nodules ringed by connective tissue. A nodule is a growth of abnormal tissue beneath the skin. These cells are close together.
  • Medulloblastoma with extensive nodularity (MBEN) contains more nodules.
  • Anaplastic medulloblastoma is made up of cells with irregular shapes.
  • Each tumor cell in large-cell medulloblastoma has a large nucleus.

Medulloblastoma can also be classified by spread of disease (metastasis):

  • M0: The tumor is in one place with no sign of spread to other parts of the body.
  • M1: Tumor cells are found in the CSF.
  • M2: The tumor has spread to the brain.
  • M3: The tumor has spread to the spine.
  • M4: The tumor has spread outside the central nervous system (CNS). Common places for spread include the bones, lungs and liver.

What are the molecular groups of medulloblastoma?

Patients have outcomes and treatment responses based on age, what the tumor looks like under a microscope, whether the tumor has spread, and molecular features. These features can vary for each molecular group. Once the doctor has determined the type of medulloblastoma, treatment is tailored to the specific group

Doctors use molecular groups to determine risk and plan the best treatment for the tumor type. Medulloblastoma has four molecular groups:

  • SHH medulloblastoma is the most common form of medulloblastoma in patients under age 3. Around two-thirds of all cases of medulloblastomas in infants are this type. It also occurs in adults over age 17. This group makes up around 30% of all medulloblastoma cases. SHH is named for the sonic hedgehog pathway that is mutated in these tumor cells. 
  • WNT medulloblastoma (pronounced “wint”) typically occurs in children ages 4 years to early adulthood. This subgroup makes up around 10% of all medulloblastoma cases. It affects males and females equally. This molecular group is named for the pathway (WNT signaling) that is mutated in these tumor cells. The pathway controls cell growth, movement and how the cell changes from one form to another. Children with WNT medulloblastomas have 5-year survival rates of 95% or better.
  • Group 3 medulloblastoma largely occurs in infants and children. This group makes up around 25% of all medulloblastoma cases. It occurs in males twice as often as in females. This group has a set of genes that are often mutated in tumor cells. Patients with Group 3 medulloblastoma are high-risk or very high-risk depending on their age and the tumor’s molecular features. These patients likely require more intense treatment, including radiation therapy.
  • Group 4 medulloblastoma is the most common form of medulloblastoma for patients of all ages. It accounts for 35-40% of all cases. This type of tumor occurs three times as often in males as in females. Group 4 tumors have few gene mutations. The cancer has usually spread by the time it is found. Group 4 tumors are considered intermediate to high-risk, depending on age and molecular features.

Learn more about the molecular groups of medulloblastoma (pdf) >

How is medulloblastoma treated?

Medulloblastoma is commonly treated with surgery to remove the tumor followed by radiation and chemotherapy. St. Jude clinicians have developed risk-based treatments based on the different molecular groups. This approach is used to raise survival rates and lower possible side effects of treatment. If the patient’s prognosis is good, a lower intensity therapy can be offered. Patients with high-risk disease may receive more intensive therapy to improve the chance of survival.

  • Surgery – is usually the first step to treating medulloblastoma. The goal is complete removal of the tumor. The surgery’s success can depend on the tumor’s location and how much can be removed safely.
  • Radiation therapy – uses high-energy X-rays or other types of radiation such as proton beam radiation to kill cancer cells or stop them from growing. The dose given depends on the stage of disease and risk category. Radiation may be combined with chemotherapy to improve outcomes.
    • Proton beam radiation is another form of radiation therapy. This type of radiation uses protons instead of X-rays. The protons can be adjusted to stop at the tumor instead of going through the body and affecting healthy tissue like X-rays can do.
  • Chemotherapy – uses powerful medicines to kill cancer cells or stop them from growing (dividing) and making more cancer cells. For young children, chemo may be offered to delay radiation until the patient is child is older. Some types of medulloblastoma may be successfully treated with only chemo.

What are the survival rates for medulloblastoma?

Medulloblastoma survival rates depend on the patient’s age, features of the tumor and how much the tumor has spread.

  • If the disease has not spread, survival rates are around 70%.
  • If it has spread to the spinal cord, the survival rate is about 60%.
  • Children younger than age 3 often have lower survival rates because options for safe and effective treatment may be limited in this age group.
  • Survival rates for specific molecular groups of medulloblastoma may vary.

Why choose St. Jude for your child’s medulloblastoma treatment?

  • The St. Jude Brain Tumor Program is a worldwide leader in medulloblastoma therapy and research. Our clinicians and researchers are regularly among the most cited in their fields.
  • At St. Jude, medulloblastoma patients take part in clinical trials that use the most advanced treatments available. Our goal is to treat every patient with the lowest number of side effects. Our clinical trials are based on years of experience and success. We have set the standard for medulloblastoma treatment, advancing cure rates and improving the understanding of the disease.
  • Our team has extensive experience in treating both new patients and those whose cancer has returned. Our international clinical trial SJMB12 has provided treatment to over 500 new patients.
  • Our team includes doctors trying to cure the disease, but also services in nutrition, rehabilitation, neurology, surgery, nursing, education, endocrinology, and psychology. This expert team supports each child through diagnosis, treatment and recovery.

Contact the Brain Tumor Team any time, 24 hours a day, 7 days a week.

Call our Brain Tumor Coordinator, Tabatha E. Doyle, RN:
(901) 595-2544

Or email us at


Associated Clinical Trials

PBTC49: Study of Savolitinib in Recurrent, Progressive or Refractory Medulloblastoma, HGG or DIPG

Phase I study of Savolitinib in Recurrent, Progressive or Refractory Medulloblastoma, High-Grade Glioma, or Diffuse Intrinsic Pontine Glioma

Diseases Treated:


High-grade glioma (HGG)

Diffuse intrinsic pontine glioma (DIPG)


  • Recurrent, refractory or progressive medulloblastoma, high-grade glioma (HGG) or diffuse intrinsic pontine glioma (DIPG)
  • Evidence of genetic activation of the MET pathway (expansion co-hort)
  • At least 5 years old and 21 years old or younger
View Trial

SJiMB21: Risk-Based Medulloblastoma Treatment for Infants and Young Children

SJiMB21: Phase 2 Study of Molecular and Clinical Risk-Directed Therapy for Infants and Young Children with Newly Diagnosed Medulloblastoma

Diseases Treated:



  • All patients with newly diagnosed medulloblastoma between birth and 3 years old
  • A select group of low-risk patients with newly diagnosed medulloblastoma between 3 and 5 years old
  • No previous radiotherapy, chemotherapy, or other treatment for the brain tumor other than corticosteroid therapy and surgery


Eligibility Exclusions:

  • Other medical disorders, such as serious infections or significant heart, lung, liver, psychiatric, or other organ problems that could make it hard to cope with the trial treatment or would interfere with the study procedure
View Trial

SJMB12: A Clinical and Molecular Risk-Directed Therapy for Newly Diagnosed Medulloblastoma/PNET

Clinical and Molecular Risk-Directed Craniospinal Irradiation and Combination Chemotherapy in Treating Younger Patients With Newly Diagnosed Medulloblastoma

Diseases Treated:

Medulloblastoma (includes all variants of medulloblastoma and posterior fossa PNET)


  • Diagnosis of newly medulloblastoma
  • At least 3 years old and younger than 22 years old (Strata W, S or N) OR
  • At least 22 years old and younger than 40 years old AND has SHH medulloblastoma (Stratum S)
  • Has not received previous treatment with radiation therapy or chemotherapy
  • Must start treatment within 36 days of surgery to remove the tumor
View Trial

SOCFUN: Social Functioning in Survivors of Pediatric Brain Tumors

Components of Social Functioning in Survivors of Pediatric Brain Tumors

Diseases Treated:

Brain tumor


This study is open only to patients at St. Jude Children’s Research Hospital.

  • Diagnosis of medulloblastoma or other brain tumor
  • Between 8 and 12 years old
  • At least 2 years after completion of therapy
  • Full-time student
  • Speaks English
View Trial

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