Conditions InDepth: Brain Tumors


A tumor is an abnormal growth of cells. Normally, cells divide in a regulated manner. If cells keep dividing when new cells are not needed, a mass of tissue forms; this is called a tumor. There are two types of tumors: benign and malignant. Benign tumors stay in one place, grow to a certain size, and then generally stop. Malignant tumors do not stop growing, and pieces of them travel to other parts of the body, where they also continue to grow.

Malignant tumors, called cancers, are nearly all fatal if not treated. The ability to cure a cancer depends upon patient and tumor-related features. Patient-related features include age, performance status, overall health, and willingness to undergo treatment. Tumor-related features include type of cancer, site of the origin of the cancer, how advanced the disease is when it is detected, and the tumor’s response to therapy

Brain Tumor

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Types of brain tumors include:


Benign tumors: These begin in brain cells and remain inside the skull. A hamartoma is a benign brain tumor.

Malignant tumors: These begin in brain cells and then travel to other parts of the body. An astrocytoma is a malignant brain tumor.


Malignant tumors: These begin in an organ other than the brain, and they travel to the brain usually through the blood. They are metastatic cancers. The word "metastatic" refers to colonies of the primary tumor that have taken up residence outside their origin.


Special tumors, such as pituitary adenomas, neuromas, spinal cord tumors, and hydatid cysts, are not covered in this report.

Meningiomas are typically benign, but because they grow inside the confined space of the meninges (the skin covering the brain tissue itself), they can cause symptoms. In this sense, they are not "benign" at all. Benign or typical meningiomas do not extend beyond the brain and, if they are found incidentally, they are generally left alone. If meningiomas are located in an area where symptoms develop, they require treatment. Less commonly, this form can be malignant, or anaplastic. These tumors can actually spread outside the brain or may grow very quickly within the brain. Malignant meningiomas almost always cause symptoms and need to be addressed with therapies.

Astrocytoma is a malignant, or cancerous, type of brain tumor. This type of tumor arises from small, star-shaped cells in the brain called astrocytes. Astrocytes are one of several types of supporting cells in the brain called glial cells. Therefore, an astrocytoma is a type of glioma.

Astrocytoma is the most common form of glioma and may occur anywhere in the brain. However, it is most commonly found in the cerebrum in adults and in the cerebellum in children.

Oligodendrogliomas are rare brain tumours that grow slowly and tend not to invade surrounding tissue to the degree that astyrocytomas do. These are most common in young adults, who often are diagnosed because they have a seizure that brings them to the attention of a physician. These tumors are uncommon, comprising only about 5% of all brain tumors.


Primary brain tumors are the second most common cancer in children and young adults, second only to leukemia. They are the third most common cancer in people between the ages of 15 and 34, fourth between the ages of 35 to 54, and much less common in older adults, where metastatic tumors predominate. Of these tumors, about a quarter are meningiomas, and most of the rest are astrocytomas.


Ionizing radiation and several hereditary diseases are the only known risk factors for developing brain tumors. The cause of the majority of primary brain cancers is unknown. Viruses and environmental factors may play a role. Although there has been a theory that electromagnetic radiation from power lines or cell phones increases the likelihood of brain tumor development, this has not been proven in any scientific investigation. The causes of secondary brain cancers are those that caused the malignancy at the site of origin (eg, lung or breast).

What are the risk factors for brain tumor?
What are the symptoms of brain tumor?
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Are there screening tests for brain tumor?
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Where can I get more information about brain tumor?


Harrison's Principles of Internal Medicine . 14th ed. McGraw-Hill; 1998.

Textbook of Clinical Neurology . WB Saunders; 1999.

The Whole Brain Atlas website. Available at: http://www.med.harvard.edu/AANLIB/home.html .

Last reviewed April 2007 by Jondavid Pollock, MD, PhD

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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