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, can be fatal if not treated. The ability to cure a cancer depends upon patient and tumor-related features. Patient-related features include:
- Performance status
- Overall health
- 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
- Tumor’s response to therapy
Types of brain tumors include:
These are tumors which start in the brain or its coverings (meninges).
Metastatic: 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 organ of origin.
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 resembles the 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 another type of glioma. They are often slower growing than astrocytomas.
Special tumors, such as pituitary adenomas, neuromas, spinal cord tumors, and hydatid cysts, are not covered in this report.
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. Gliomas are the most common group of primary brain tumors in adults.
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).
Goetz CG, Pappert EJ. Textbook of Clinical Neurology. Philadelphia, PA: WB Saunders; 1999.
Harrison TR, Fauci AS. Harrison's Principles of Internal Medicine. 14th ed. New York, NY: McGraw-Hill; 1998.
The Whole Brain Atlas website. Available at: http://www.med.harvard.edu/AANLIB/home.html .
Last reviewed February 2009 by
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