The human body is made up of specialized cells which grow and divide in an orderly fashion. When these cells become unable to control their growth, they divide too often and without order. The extra cells form a mass called a tumor. Every year, over 16000 people are diagnosed with a benign or malignant brain tumor. Benign tumors do not contain cancer cells and do spread to nearby tissue, although they can press on the brain and cause symtpoms. Life-threatening malignant tumors do contain cancer cells. They grow quickly and invade other tissue. The tumors may grow "roots" into healthy brain tissue. Malignant tumors without roots are called "encapsulated" tumors. Brain tumors are refered to by grade, ranging from the lowest grade I to the highest grade IV. Cells from a high grade tumor look more abnormal and grow faster than cells from lower grade tumor.

Brain tumors are not contagious, but the cause of them is not known. The tumors usually occur between the ages of 3 and 12 or between the ages of 40 and 70. Some types of brain tumors are more frequent among people working in certain industries (oil refining, rubber manufacturing, drug manufacting, chemistry, etc.). Exposure to viruses may also be a risk factor in brain cancer. Hereditary may also be a possible cause of brain tumors.

Tumors than originate in the brain are called primary tumors. Primary tumors are classified by the tissue that they originate in. The most common type of brain tumors are gliomas, which form in the glial tissue. There are several types of gliomas. One form is the astrocytoma that arises from small, star-shaped cells called astrocytes. They grow anywhere in the brain or spinal cord. Brain stem gliomas occur in the brain stem and are mostly high grade astrocytomas. These tumors usually are unremovable. Ependymomas develop in the lining of the ventricles or in the spinal cord. They are most common in childhood or adolescence. Oligodendrogliomas originate in myelin-producing cells, usually in the cerebrum. They grow slowly and do not spread to other tissue. They mostly occur in middle-aged adults.

Several brain tumors do not begin in the glial cells. For example, medulloblastomas seem to develop from primitive neuroblasts that normally disappear after birth. Most medulloblastomas occur in cerebellum of male children. Meningiomas grow in the meninges and are usually benign. They grow slowly, so the brain adapts to its existence. They may grow fairly large before causing symptoms. These tumors are most common in 30-50 year old women. Schwannomas are benign tumors that originate in the Schwann cells, which produce myelin to protect the acoustic nerve. These occur mostly in adults and are twice as likely to be found in females. Craniopharyngiomas form in the pituatiary gland by the hypothalamus and are most often found in children and adolescents. They are usually benign, but they can press or damage the hypothalamus. Germinomas are also found in the brain. These germ cell tumors develop from primitive sex cells. Pineal region tumors are also found in the brain around the pineal gland. It can be a slow- growing pineocytoma or a fast-growing pineoblastoma. These tumors usually cannot be removed.

Secondary brain tumors are those that form with the metastasis (spread) of cancer. The cells that spread to the brain are not the same as primary brain cancer cells. For example, if cancer spread from the lung to the brain, the cells would be called metastatic lung cancer because the cells would be abnormal lung cells and not abnormal brain cells. Treatment for secondary tumors depend on where the cancer began, the extent of the spread, and the patient's age, health, and response to other treatment.

The symptoms of brain tumors vary with the size and position of the tumor. Tumors may damage vital tissue and put pressure on the brain. They may also cause a swelling and a buildup of fluid around the tumor (edema). Hydrocephalus may occur when the tumor blocks the flow of cerebrospinal fluid, making it build up in the ventricles.

Brain tumors can be diagnosed by two methods: CAT scan or MRI. A CAT (CT) scan is a series of pictures of the brain that are created by a computer hooked up to an x-ray machine. An MRI (magnetic resonance imaging) show pictures of the brain by using a powerful magnet linked a computer. MRI is useful because it can make tissue underneath the skull visible. Some other tests are also used to diagnose brain tumors. Skull x-rays show changes in the skull caused by tumors, as well as clacium deposits that are found in some tumors. Brain scans can show areas of abnormal growth in the brain after a dye in injected into a vein and absorbed by the tumor. And angiogram (arteriogram) is a series of x-rays taken after a dye is injected into an artery. The dye flows through blood vessels in the brain and shows where the tumor is. A myelogram is a spine x- ray for which a dye is injected into the cerebrospinal fluid in the spine. This test shows where in the spine a tumor is present.

Brain tumors can be treated with surgery, radiation therapy, and chemotherapy. Surgery is most used to treat the tumors. A neurosurgeon makes an opening in the skull to remove a tumor. This is called craniotomy. However, it may not be possible to remove the entire tumor, so only part of it is removed to relieve pressure. If the tumor cannot removed at all, a biopsy may be performed to find out what type of cells are present and which type of treatment would be best. Radiation therapy uses high-pwer rays to damage the cancer cells and prevent them from spreading. It is usually used when surgery is not sufficient. Chemotherapy uses drugs to kill cancer cells. The drugs can be given by mouth or by injection into a blood vessel or muscle. Intrathecal chemotherapy involves injecting blood into the cerebrospinal fluid.