A primary brain tumor is a group (mass) of abnormal cells that start in the brain. This article focuses on primary brain tumors in children.

The cause of primary brain tumors is unknown. Primary brain tumors may be:

• Benign (not cancerous)
• Invasive (spread to nearby areas)
• Located in only a small area
• Malignant (cancerous)

Brain tumors are classified depending on the exact site of the tumor, the type of tissue involved, and whether or not it is cancerous. Brain tumors can directly destroy brain cells. They may also indirectly damage cells by pushing on other parts of the brain. This leads to swelling and increased pressure within the skull.

Tumors may occur at any age, but many specific tumors are more common at a certain age. However, most brain tumors are rare in the first year of life. Some of the most common childhood brain tumors include:

• Astrocytomas
• Brain stem gliomas
• Ependymomas
• Medulloblastomas

SPECIFIC TUMOR TYPES

Astrocytomas are usually noncancerous, slow-growing cysts. They most commonly develop in children ages 5 - 8.

Brainstem gliomas occur almost only in children. The average age of development is about 6 years old. The tumor may grow very large before triggering symptoms.

Ependymomas make up about 8 - 10% of pediatric brain tumors. The tumors are located in tiny passageways (ventricles) in the brain, and block the flow of cerebrospinal fluid (CSF).

Medulloblastomas are the most common type of childhood brain cancer. They occur more often in boys than girls, usually around age 5. Most medulloblastomas occur before the age of 10.