Medulloblastoma is a tumor that grows in a part of the brain called the cerebellum. The cerebellum is located at the base of the skull, above the brainstem. It is the part of the brain that controls balance, coordination, and other motor functions.

Medulloblastoma is the most common cancerous brain tumor in children. It makes up 20 percent of all pediatric brain tumors. There are between 250 to 500 cases of medulloblastoma found each year in the United States. The tumor is mostly found in children between the ages of 5 and 16, but can occur in older teenagers and even in adults.

Many children can be cured of medulloblastoma with the right treatment. Doctors used to classify medulloblastoma as standard or high-risk, based on factors such as how much of the tumor could be removed surgically, what the tumor looked like under the microscope, and how much the tumor had spread.

However, in recent years, it was discovered that there are actually four different types of medulloblastoma, based on genetic changes within the tumor.