A brain tumor is an abnormal growth of tissue in the brain. Unlike other tumors, brain tumors spread by local extension and rarely metastasize (spread) outside the brain. A benign brain tumor is composed of non-cancerous cells anddoes not spread beyond the part of the brain where it originates. A brain tumor is considered malignant if it contains cancer cells, or if it is composedof harmless cells located in an area where it suppresses one or more vital functions.
Each year, more than 17,000 brain tumors are diagnosed in the United States.About half are benign, but may be in life-threatening locations. The rest aremalignant and invasive.
Benign brain tumors, composed of harmless cells, have clearly defined borders, can usually be completely removed, and are unlikely to recur. Benign braintumors do not infiltrate nearby tissues but can cause severe pain, permanentbrain damage, and death. Benign brain tumors sometimes become malignant.
Malignant brain tumors do not have distinct borders. They tend to grow rapidly, increasing pressure within the brain and can spread in the brain or spinalcord beyond the point where they originate. It is highly unusual for malignant brain tumors to spread beyond the central nervous system (CNS).
Primary brain tumors originate in the brain. They represent about 1% of all cancers and 2.5% of all cancer deaths. Approximately 25% of all cancer patients develop secondary or metastatic brain tumors when cancer cells spread fromanother part of the body to the brain. Metastatic brain tumors can develop onany part of the brain or spinal cord. Brain tumors can develop at any age, but are most common in children between the ages of 3-12, and in adults aged 40-70.
The name of a brain tumor describes where it originates, how it grows, and what kind of cells it contains. A tumor in an adult is also graded or staged according to how malignant it is, how rapidly it is growing, how likely it is to invade other tissues, and how closely its cells resemble normal cells.
Low-grade brain tumors usually have well-defined borders. Some low-grade brain tumors are enclosed in cysts. Low-grade brain tumors grow slowly, if at all. They may spread throughout the brain, but rarely metastasize to other partsof the body.
Mid-grade and high-grade tumors grow more rapidly than low-grade tumors. Described as "truly malignant," these tumors usually infiltrate healthy tissue. Their growth pattern makes it difficult to remove the entire tumor, and thesetumors recur more often than low-grade tumors.
A single brain tumor can contain several different types of cells. The tumor's grade is determined by the highest-grade (most malignant) cell detected under a microscope, even if most of the cells in the tumor are less malignant. An infiltrating tumor is a tumor of any grade that grows into surrounding tissue.
The cause of primary brain tumors is unknown, but people who work with rubberand certain chemicals have a greater risk of developing them. There is no evidence that head injury causes brain tumors, but researchers are trying to determine the relationship, if any, between brain tumors and viruses, family history, and long-term exposure to electromagnetic fields.
Symptoms do not usually appear until the tumor grows large enough to displace, damage, or destroy delicate brain tissue. When that happens, the patient may experience headaches that become increasingly painful and are most painfulwhen lying down, nausea and vomiting, seizures dizziness, loss of coordination or balance, personality changes, sudden loss of vision, memory loss speechproblems, sensory changes, mental impairment, and/or weakness or paralysis onone side of the body.
When a patient has one or more of these symptoms, a primary care physician will perform a complete physical examination, take a detailed medical history,and conduct a basic neurologic examination.
If the results of these examinations suggest a patient may have a brain tumor, a neurologist recommends some or all of these additional diagnostic tests:computed tomography scan (CT scan) to reveal brain abnormalities, magnetic resonance imaging (MRI) to detect tumors beneath the bones of the skull; electroencephalography (EEG) to measure electrical activity in the brain; x rays toreveal any distortion in the bones of the skull; angiography to outline a tumor and the blood vessels that lead to it; a brain scan to identify and record the location of abnormal cells in the brain; x rays of the spine to detecta spinal cord tumor, or a lumbar puncture (spinal tap) to obtain spinal fluid, which may contain tumor cells.
Interpreting these images and the results of laboratory analysis allows a neurologist to determine whether a tumor is present, but microscopic examinationof tumor tissue (a biopsy) is the only way to identify the kind of cells itcontains.
Surgery is the treatment of choice for accessible brain tumors that can be removed without causing serious neurologic damage. Patients whose benign braintumors can be completely removed may not require any additional treatment, although periodic examinations are recommended. Because surgeons cannot be surethat every bit of an infiltrating or metastasizing tumor has been removed, radiation and chemotherapy are used to destroy cells that may have escaped thescalpel.
If a tumor cannot be completely removed, removing a portion of it (debulking)can alleviate the patient's symptoms, enhance the sense of well-being, and increase the effectiveness of other treatments.
Radiation therapy is often a very effective treatment used to help destroy tumor cells. A number of drugs have been developed and found to be effective ways to fight brain tumors. One or more cancer-killing drugs may be taken by mouth or injected into a blood vessel, muscle, or the cerebrospinal fluid. Chemotherapy may be used with radiation and surgery as part of a patient's initial treatment, or used alone to treat tumors that recur.
The chances of a patient's recovery depend on where the tumor is located andwhat type of cells it contains. A patient whose tumor is discovered early andremoved completely may make a full recovery, but the surgery itself can harmor destroy normal brain tissue and cause problems with thought, speech, andcoordination, seizures, weakness, or personality changes.
If a brain tumor cannot be cured, treatment is designed to make the patient as comfortable as possible and preserve as much of his neurologic functioningas possible. Brain tumors that cannot be removed can cause irreversible braindamage and death.
Research efforts center on ways to empower chemotherapy drugs to penetrate the blood-brain barrier (which protects the central nervous system by separating the brain from blood circulating throughout the body), and attack cancer cells that have infiltrated tissue inside it.
Brain tumor researchers are also investigating less invasive surgical procedures, methods of incorporating chemotherapy drugs into tumor cells to reduce the need for radiation, and laboratory techniques that enable physicians to select the chemotherapy drugs most likely to kill particular types of tumors. Also being researched is gene therapy, in which genetically engineered material is transported to tumor cells by viruses that infect tumor cells and eitherconvert them to normal cells, stop their growth, or kill them.