A brain tumor is a mass of abnormal cells growing in the brain. Despite its frightening name, not all brain tumors are cancerous or fatal.
A brain tumor is a clump of abnormal tissue that can be found anywhere in the brain. The brain and spinal cord form the central nervous system, which controls bodily functions. Some of these, such as walking and talking, are voluntary or intentional actions. Others, such as food digestion and heart rate, are involuntary or automatic functions. The central nervous system manages the automatic functions with the help of hormones secreted through numerous glands that are part of the endocrine system * . Besides these tasks, the central nervous system also controls people's senses, emotions, thoughts, memory, and personality.
Brain tumors are categorized in two ways: first, by how they look during imaging tests that create pictures of the brain and by how the tissue appears under a microscope; and second, according to whether they formed in the brain or spread there from another part of the body.
Benign brain tumors have clearly defined edges and contain cells that look healthy, just like normal cells. They tend to grow slowly, are not likely to spread, and rarely grow back once they are removed. The word benign means harmless or not cancerous. Benign tumors can cause impairment if they grow large enough to push against parts of the brain and interfere with normal brain function.
Malignant brain tumors are also called brain cancer. They are made up of abnormally shaped cells and can have irregular borders. They tend to grow quickly and invade surrounding brain tissue. Although the tumors may spread to the spinal cord, they generally do not spread to other parts of the body. In some cases, one tumor may contain a combination of nearly normal and extremely abnormal cells.
Primary brain tumors begin in the tissues of the brain and may be either benign or malignant. According to the American Brain Tumor Association, about 70,000 people in the United States receive a diagnosis of a primary brain tumor each year, and about 60 percent of these are benign. Of the 70,000 total, approximately 4,600 occur in individuals under 20 years of age.
Secondary brain tumors are actually formed from cancer cells that have traveled to the brain from another part of the body. For example, cells from tumors in the lung or breast can spread to the brain and cause new tumors to grow. Secondary brain tumors are always malignant.
In addition, brain tumors are classified by the type of brain cell that became a tumor, with medical names such as astrocytoma (as-tro-sy-TOmuh), glioma (glee-O-muh), ependymoma (e-pen-di-MO-muh), germinoma (jer-mi-NO-muh), medulloblastoma (med-yoo-lo-blas-TO-muh), meningioma (me-nin-jee-O-muh), and neuroblastoma (noor-o-blas-TOmuh). Their common ending “-oma” means “tumor,” and the remainder of the word indicates the part of the brain where the tumor forms. For example, the second-most-common type of brain tumor, meningioma, forms in the meninges, which are the membranes that cover the brain and spinal cord. Gliomas, the most common type of brain tumor, form in the supportive tissue of the brain, called the glia.
Doctors cannot explain why some individuals develop brain tumors. Even though a tumor can spread within the brain, it cannot spread from one person to another; in other words, brain tumors are not contagious.
Researchers have found that some brain tumors are more common in people who are frequently exposed to certain chemicals used to manufacture rubber, pharmaceuticals, crude oil and petroleum, and nuclear fuel and weapons, as well as chemicals used on farms. They have investigated whether certain viruses may contribute to brain tumor development.
Heredity is another possible cause. Because brain tumors sometimes occur in several members of the same family, researchers continue to study possible causes, including family syndromes that cause multiple tumors in the body. As many as 5 percent of brain tumors likely occur because of family history.
In addition, some studies have linked cellular phone usage to increased risk, but many others have shown no such connection.
In addition to asking about symptoms, doctors perform a neurological exam, which involves different tests of vision and eye movement, hearing, reflexes, balance and coordination, memory, thinking ability, and other functions controlled by the brain.
Doctors are also likely to order imaging tests such as a computed tomography * (CT) scan or a magnetic resonance imaging * (MRI) scan. Among other possible types of tests is an angiogram * . This procedure helps doctors evaluate the blood vessels leading to a tumor.
Once a tumor is found, doctors can confirm the diagnosis only with a biopsy * . In some cases, doctors take a sample of the cerebrospinal fluid that surrounds the brain and spinal cord, and then send the fluid to be examined under a microscope. More commonly, surgeons remove part or all of the tumor through biopsy and then send the tissue to a laboratory for analysis. To get to a brain tumor, doctors open part of the skull (a procedure called craniotomy), or they may drill a small hole in the skull and use a needle to take a tissue sample. Both before and sometimes during the operation, surgeons use computerized images of the brain to help them locate the tumor and avoid the nearby healthy tissues that are essential for normal function. Doctors might have special molecular testing * conducted on the tumor sample to identify genes that indicate cancer or a family syndrome that causes brain tumors.
Surgery, radiation therapy, and chemotherapy are the three most common treatments for a brain tumor, but the type of tumor, its location, and the patient's age often determine how these treatments are used. One of the most important factors for determining treatment is knowing whether a brain tumor is cancerous or benign. Before the process starts, most patients receive medications to relieve any swelling in the brain and control the seizures that often occur with brain tumors.
Radiation therapy (also called radiotherapy) is the use of high-powered radiation to destroy cancer cells or stop them from growing. It is often used to destroy tumor tissue that cannot be removed with surgery or to kill cancer cells that may remain after surgery. Radiation therapy can be used when surgery is not possible. External radiation comes from a large machine, while internal radiation involves implanting radioactive material directly into the tumor. Even though the radiation is focused on the tumor, some of the surrounding healthy tissue might be damaged as well. Doctors avoid giving radiation to very young children, especially those under three years of age, because their brains are still developing. These children are often treated with chemotherapy until they are old enough to have radiation therapy.
During chemotherapy, doctors give anticancer drugs by mouth; by injection into a blood vessel or muscle; or intravenously into a blood vessel. Because the body automatically tends to prevent chemicals and other foreign substances from entering the brain and spinal cord (a kind of “self-defense” mechanism), doctors may need to inject them directly into the spinal fluid.
Research studies called clinical trials evaluate numerous other treatments for brain tumors. For example, researchers can test biological therapies that try to “supercharge” the body's disease-fighting immune system against the tumor. They also test drugs that can prevent tumors from creating the new blood vessels they need to keep growing. In the United States, the National Cancer Institute has formed groups of doctors nationwide who work together to find new treatments for brain tumors in children and adults.
Sometimes, the tumor or the treatment damages some of the nearby healthy brain tissue that controls physical and mental function. Patients need to work with a special therapist if they are having trouble using their arms or legs, maintaining balance, speaking, swallowing, or expressing their thoughts. They may feel tired or depressed, and they may experience personality changes. Children may find that they have problems with learning or remembering what they learn when they return to school.
See also Brain Cancer • Cancer: Overview • Epilepsy • Tumor
Ellison, David, et al. Neuropathology: A Reference Text of CNS Pathology. 3rd ed. Philadelphia: Mosby, 2013.
Gray, Françoise, Charles Duyckaerts, and Umberto De Girolami. Escourolle & Poirier's Manual of Basic Neuropathology. 5th ed. New York: Oxford University Press, 2013.
American Society of Clinical Oncology. “Brain Tumor: Overview.” Cancer.net . http://www.cancer.net/cancer-types/brain-tumor/overview (accessed March 15, 2016).
American Brain Tumor Association. 8550 W Bryn Mawr Ave., Suite 550, Chicago, IL 60631. Telephone: 773-577-8750. Toll-free: 800-886-ABTA (2282). Website: http://www.abta.org (accessed March 15, 2016).
National Brain Tumor Society. 55 Chapel St., Suite 200, Newton, MA 02458. Telephone: 617-924-9997. Website: http://braintumor.org (accessed March 15, 2016).
National Cancer Institute. BG 9609 MSC 9760, 9609 Medical Center Dr., Bethesda, MD 20892-9760. Toll-free: 800-422-6237. Website: http://www.cancer.gov (accessed March 15, 2016).
* endocrine system is a system of ductless glands, including the thyroid and pituitary, that secrete hormones and control many bodily functions.
* computed tomography (CT) (kom-PYOO-tid toe-MAH-gruhfee) is a technique in which a machine takes many crosssectional x-rays of the body to create a three-dimensional picture.
* magnetic resonance imaging (MRI) produces computerized images of internal body tissues based on the magnetic properties of atoms within the body.
* angiogram (an-GEE-oh-gram) is an imaging examination that uses dye injected into a blood vessel as a highlighter to show blood flow.
* biopsy (by-op-SEE) is a procedure used to collect a sample of tumor cells for study in a laboratory. A doctor can use a needle or surgery to collect the sample.
* molecular (mo-LECK-you-ler) testing is a way to study tumor cells in a laboratory to look for patterns in the cells' DNA. It can help diagnose tumors and help doctors better plan treatment.