Brain Tumors: Primary - Introduction

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Ependymomas are derived from ependymal cells, which line the ventricles (fluid-filled cavities) in the lower part of the brain and the central canal of the spinal cord. They are one of the most common types of brain tumor in children. They can also occur in adults in their 40s and 50s. Ependymomas are divided into four categories: Myxopapillar ependymomas (grade I), subependymomas (grade I), ependymomas (grade II), and anaplastic aependymomas (grades III and IV).

Mixed gliomas contain a mixture of malignant gliomas. About half of these tumors contain cancerous oligodendrocytes and astrocytes.

Gliomas may also contain cancer cells derived from brain cells other than glial cells.

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Location of Gliomas. Gliomas are also described by the location of the tumor. Examples include:

• Brain stem gliomas develop in the lowest portion of the brain. The brain stem connects the cerebrum (the largest part of the brain) to the spinal cord. Between 10 - 20% of brain tumors in children are brain stem gliomas. Most of these tumors are astrocytomas.
• Cerebellar astrocytomas occur in the cerebellum part of the brain, which controls balance and coordination.
• Optic gliomas occur in the optic nerve and other parts of the eye. They primarily affect children younger than age 10. About 20% of children with the genetic disorder neurofibromatosis 1 (NF-1) develop optic gliomas. Pilocytic astrocytoma and fibrillary astrocytoma are common types of optic gliomas.

Click the icon to see an image of the function of the brain stem.

Click the icon to see an image of the function of the cerebellum.

Click the icon to see an image of the optic nerve.

Primary Non-Glioma Brain Tumors

Malignant types of non-glioma brain tumors include:

Medulloblastomas. Medulloblastomas are always located in the cerebellum, which is at the base and toward the back of the brain. These fast-growing high-grade tumors represent about 15 - 20% of pediatric brain tumors and 20% of adult brain tumors.

Pituitary Adenomas. Pituitary tumors (also called pituitary adenomas) comprise about 10% of primary brain tumors and are often benign, slow-growing masses in the pituitary gland. They are more common in women than men.