Table of Contents
Astrocytomas are primary brain tumors derived from astrocytes, which are star-shaped glial cells. Astrocytomas account for about 60% of all malignant primary brain tumors. Astrocytoma tumor types by grade include:
- Grade I. Pilocytic astrocytoma is one of the most common types of glioma in children
- Grade II. Diffuse astrocytoma (also called low-grade astrocytoma) typically occurs in men and women ages 20 - 60
- Grade III. Anaplastic astrocytoma typically occurs in adults ages 30 - 60 and is more common among men than women.
- Grade IV. Glioblastoma multiforme (GBM), also called glioblastoma, accounts for about 50% of all astrocytomas and is one of the deadliest types of brain tumors. These highly malignant aggressive tumors grow rapidly. They are most common in older adults (ages 50 - 70), particularly men. Only about 10% of childhood brain tumors are glioblastomas.
Oligodendrogliomas develop from oligodendrocyte glial cells, which form the protective coatings around nerve cells. Oligodendrogliomas are classified as either low-grade (grade II) or anaplastic (grade III). Pure oligodendrogliomas, however, are rare. In most cases they occur in mixed gliomas. Oligodendrogliomas usually occur in younger and middle-aged adults.
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.
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.
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Click the icon to see an image of the function of the brain stem. |
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Click the icon to see an image of the function of the cerebellum. |
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Click the icon to see an image of the optic nerve. |
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Review Date: 10/21/2010
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine,
Harvard Medical School; Physician, Massachusetts General Hospital.
Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M.,
Inc.
A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org)
