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Health A-Z

Medical Content Created by the Faculty of the
Harvard Medical School

What Is It?

A brain tumor is a mass of abnormally growing cells in the brain or skull. It can be benign (noncancerous) or malignant (cancerous). Unlike other cancers, a cancer arising from brain tissue (a primary brain cancer) rarely spreads. Whether benign or malignant, all brain tumors are serious. A growing tumor eventually will compress and damage other structures in the brain.

There are two categories of brain tumors: primary and secondary. Primary tumors start in brain tissue, while secondary tumors spread to the brain from another area of the body. Primary tumors are classified by the tissue in which they begin:

  • Gliomas, the most common primary tumors, start in the brain's glial (supportive) tissue. There are several types of gliomas, and they can vary in their aggressiveness and response to treatment. Glioblastoma multiforme is a fast-growing, higher-grade tumor that can arise from a lower-grade glioma.

  • Medulloblastomas come from early embryonic cells and more commonly occur in children.

  • Meningiomas are related to cells in the membranes surrounding the brain and spinal cord. They are usually benign, but can come back (recur) after treatment.

Secondary tumors most commonly arise from the lungs or breast. Other cancers, especially melanoma (a type of skin cancer), renal cell cancer (a type of kidney cancer), and lymphoma (a cancer of the immune system) can spread to the brain. When this happens, the cancer is the same as the original cancer. For example, lung cancer that spreads to the brain is known as metastatic lung cancer, because the tumor's cells resemble abnormal lung cells. Secondary brain tumors are much more common than primary tumors.

Although brain tumors can occur at any age, they most commonly affect adults 40 to 70 years old and children 3 to 12 years of age. Whether the use of cellular phones contributes to the development of brain tumors, especially in children, has sparked debate. The issue is far from resolved, and additional research is needed.

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From Health A-Z, Harvard Health Publications. Copyright 2007 by the President and Fellows of Harvard College. All rights reserved. Written permission is required to reproduce, in any manner, in whole or in part, the material contained herein. To make a reprint request, contact Harvard Health Publications. Used with permission of StayWell.

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