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Types of Cancer - Brain Cancer
The brain is one of the most important organs in the body. It is the source of our movements, our vital activities, our thoughts, and our sensations of the world around us.
Types of Cancer
What is a brain tumor?
When cells inside the brain begin to replicate at an abnormal rate, a tumor is formed. Tumors can be either benign or malignant. Benign tumors are usually not cancer, do not invade nearby tissue, and when removed do not recur. Malignant tumors are made up of cancer cells. They can press on areas of the brain and disrupt its function, and may invade and grow into the healthy tissue around them.
Doctors refer to some brain tumors by grade - from low grade (grade I) to high grade (grade IV). The grade of a tumor refers to the way the cells look under a microscope. Cells from higher grade tumors are more abnormal looking and generally grow faster than cells from lower grade tumors; higher grade tumors are more malignant than lower grade tumors.
Types of Brain Tumors
Tumors that begin in brain tissue are known as primary brain tumors and are classified by the type of tissue in which they begin. The most common brain tumors are gliomas, which begin in the glial (supportive) tissue. There are several types of gliomas:
- Astrocytomas arise from small, star-shaped cells called astrocytes. They may grow anywhere in the brain or spinal cord. In adults, however, astrocytomas most often arise in the cerebrum.
- Brain stem gliomas occur in the lowest, stemlike part of the brain. The brain stem controls many vital functions. Tumors in this area generally cannot be removed. Most brain stem gliomas are high-grade astrocytomas.
- Ependymomas usually develop in the lining of the ventricles. They may also occur in the spinal cord.
- Oligodendrogliomas arise in the cells that produce myelin, the fatty covering that protects nerves. These tumors usually arise in the cerebrum. They grow slowly and usually do not spread into surrounding brain tissue. Oligodendrogliomas are rare and occur most often in middle-aged adults.
There are other types of brain tumors that do not begin in glial tissue. Some of the most common are described below:
- Medulloblastomas were once thought to develop from glial cells. However, recent research suggests that these tumors develop from primitive (developing) nerve cells that normally do not remain in the body after birth. For this reason, medulloblastomas are sometimes called primitive neuroectodermal tumors (PNET).
- Meningiomas grow from the meninges. They are usually benign. Because these tumors grow very slowly, the brain may be able to adjust to their presence; meningiomas often grow quite large before they cause symptoms. They occur most often in women between 30 and 50 years of age.
- Schwannomas are benign tumors that begin in Schwann cells, which produce the myelin that protects the acoustic nerve - the nerve of hearing. These tumors affect women twice as often as men.
- Craniopharyngiomas develop in the region of the pituitary gland near the hypothalamus. They are usually benign; however, they are sometimes considered malignant because they can press on or damage the hypothalamus and affect vital functions.
- Germ cell tumors arise from primitive (developing) sex cells, or germ cells. The most frequent type of germ cell tumor in the brain is the germinoma.
- Pineal region tumors occur in or around the pineal gland, a tiny organ near the center of the brain. The tumor can be slow growing (pineocytoma) or fast growing (pineoblastoma). The pineal region is very difficult to reach, and these tumors often cannot be removed.
Treatment
Treatment for a brain tumor depends on a number of factors. Among these are the type, location, and size of the tumor, as well as the patient's age and general health. Brain tumors are treated with surgery, radiation therapy, and chemotherapy; depending on the patient's needs, several methods may be used.
Before treatment begins, most patients are given steroids, which are drugs that relieve swelling (edema). They may also be given anticonvulsant medicine to prevent or control seizures. If hydrocephalus is present, the patient may need a shunt to drain the cerebrospinal fluid. A shunt is a long, thin tube placed in a ventricle of the brain and then threaded under the skin to another part of the body, usually the abdomen. It works like a drainpipe: Excess fluid is carried away from the brain and is absorbed in the abdomen. (In some cases, the fluid is drained into the heart.)
Surgery is the usual treatment for most brain tumors. To remove a brain tumor, a neurosurgeon makes an opening in the skull. This operation is called a craniotomy. Whenever possible, the surgeon attempts to remove the entire tumor. However, if the tumor cannot be completely removed without damaging vital brain tissue, the doctor removes as much of the tumor as possible. Partial removal helps to relieve symptoms by reducing pressure on the brain and reduces the amount of tumor to be treated by radiation therapy or chemotherapy.
Some tumors cannot be removed. In such cases, the doctor may do only a biopsy. A small piece of the tumor is removed so that a pathologist can examine it under a microscope to determine the type of cells it contains. This helps the doctor decide which treatment to use.
Sometimes, a biopsy is done with a needle. Doctors use a special headframe (like a halo) and CT scans or MRI to pinpoint the exact location of the tumor. The surgeon makes a small hole in the skull and then guides a needle to the tumor. (Using this technique to do a biopsy or for treatment is called stereotaxis.)
Many patients and their families want to learn all they can about brain tumors and the treatment choices so they can take an active part in decisions about medical care. The doctor is the best person to answer these questions. When discussing treatment, the patient may want to talk with the doctor about research studies of new treatment methods. Such studies, called clinical trials, are designed to improve cancer treatment. More information about clinical trials is in the Clinical Trials section.
Researchers are finding better ways to treat brain tumors, and the chances of recovery keep improving. Still, it is natural for patients and their families to be concerned about the future. There are many resources available both on and off the web for patients and their families. Links to some good websites can be found on our web resources page, or check out our recommended reading list for patients and their families.