Mesothelioma (me-zo-thee-le-O-muh), also called malignant * mesothelioma, is a rare, deadly cancer * of the mesothelium * —the tissue that lines the lungs, stomach, heart, and other organs. Most mesotheliomas are caused by exposure to asbestos.
Mesothelium is the two-layered membrane * that covers most of the organs of the body. It produces a lubricating fluid between the layers that cushions the organs and permits movement. Mesotheliomas can originate in four different types of mesothelium:
There are three types of mesothelioma:
Although most people who develop mesothelioma have lived or worked where they may have inhaled or swallowed asbestos, the cancer can take 20 to 50 years to develop. Household members of people who worked with asbestos are also at risk for mesothelioma. However, many people with prolonged asbestos exposure never develop the disease, whereas some people with no known exposure do. There is some evidence that genetic * susceptibility * may play a role in mesothelioma. Some studies have suggested the possibility that exposure to simian virus * 40 (SV40) may increase one's risk for mesothelioma. Some injectable polio vaccines manufactured between 1955 and 1963 were contaminated with SV40, potentially affecting an estimated 10 to 30 million people.
Although it remains a relatively rare cancer, the incidence *
Early symptoms of mesothelioma are nonspecific and often overlooked. More than half of people with pleural mesothelioma complain of pain in the lower back or side of the chest. Other symptoms of mesothelioma include:
Symptoms of peritoneal mesothelioma include:
Mesothelioma is rare, and misdiagnosis is not unusual because the symptoms are similar to other diseases, including lung cancer. A history of asbestos exposure may suggest mesothelioma. A physical exam or imaging tests can detect fluid in the chest, abdominal cavity, or pericardium.
Other procedures for diagnosing mesothelioma include:
Because it is difficult to distinguish mesothelioma from other cancers by the appearance of the cells, laboratory tests look for markers present on mesothelioma cells.
Biopsies * used to diagnose mesothelioma include:
Following a diagnosis of mesothelioma, additional imaging tests are performed to stage the cancer and determine if it has spread and, if so, where. Stage I mesothelioma is localized in the lining of the chest wall and possibly the linings of the lungs, diaphragm * , or pericardium around the heart on the same side of the chest.
Advanced mesothelioma is staged as follows:
Because mesothelioma is not a single tumor * mass, it is usually not possible to remove it completely by surgery and/or radiation therapy * . If the cancer is localized and the patient is otherwise in good health, curative surgery may be attempted. Extrapleural pneumonectomy removes one lung, the diaphragm, part of the chest lining, and the pericardium. The diaphragm and pericardium are reconstructed with prosthetic material. However, the cancer cells tend to spread and are difficult to detect. Thus, surgery may extend life but is unlikely to cure mesothelioma.
Radiation therapy is sometimes used as the primary treatment, as an adjuvant (a support) to surgery, or as palliative treatment. Chemotherapy * for mesothelioma is palliative and is usually administered intravenously or directly into the chest or abdominal cavity.
Mesothelioma is usually not diagnosed until the cancer is quite advanced. The average survival time at diagnosis is one year for approximately 40 percent of cases. The five-year survival rate is about 10 percent, which is significantly higher than in earlier decades. Most patients die of complications related to mesothelioma, such as lung failure, heart problems, or stroke * .
Although not all mesotheliomas have been connected to asbestos, avoiding such exposure is clearly the best prevention. Precautionary measures should be taken in performing any work that may involve asbestos exposure, particularly demolition of old buildings. It is often more dangerous to remove asbestos-containing materials than to leave them in place. If they are removed, the work should be performed by a qualified contractor.
See also Cancer: Overview • Environmental Diseases: Overview
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* malignant (ma-LIG-nant) refers to a condition that is severe and progressively worsening.
* cancer is a condition characterized by abnormal overgrowth of certain cells, which may be fatal.
* mesothelium (me-zo-THEE-leum) is epithelium derived from embryonic mesoderm that lines the body cavities.
* membrane (MEM-brain) is a thin layer of tissue that covers a surface, lines a cavity, or divides a space or organ.
* peritoneum is the membrane that lines the abdominal cavity.
* abdomen (AB-do-men), commonly called the belly, is the portion of the body between the thorax (THOR-aks) and the pelvis.
* testicles (TES-tih-kulz) are the paired male reproductive glands that produce sperm.
* genetic (juh-NEH-tik) refers to heredity and the ways in which genes control the development and maintenance of organisms.
* susceptibility (su-sep-ti-BIL-i-tee) means having less resistance to and higher risk for infection or disease.
* virus (VY-rus) is a tiny infectious agent that can cause infectious diseases. A virus can only reproduce within the cells it infects.
* incidence means rate of occurrence.
* inflammation (in-fla-MAY-shun) is the body's reaction to irritation, infection, or injury that often involves swelling, pain, redness, and warmth.
* DNA or deoxyribonucleic acid (dee-OX-see-ry-bo-nyoo-klay-ik AH-sid) is the specialized chemical substance that contains the genetic code necessary to build and maintain the structures and functions of living organisms.
* clotting is the process by which the body forms a thickened mass of blood cells and protein to stop bleeding.
* anemia (uh-NEE-me-uh) is a blood condition in which there is a decreased hemoglobin in the blood and, usually, fewer than normal numbers of red blood cells.
* trachea (TRAY-kee-uh), also called the windpipe, is the firm, tubular structure that carries air from the throat to the lungs.
* biopsies (BI-op-seez) are tests in which small samples of skin or other body tissue are removed and examined for signs of disease.
* aspiration (as-puh-RAY-shun) is the sucking of fluid or other material out of the body, such as the removal of a sample of joint fluid through a needle inserted into the joint.
* diaphragm (DY-a-fram) is the muscle that separates the chest and abdominal cavities. It is the chief muscle used in breathing.
* lymph nodes (LIMF) are small, bean-shaped masses of tissue containing immune system cells that fight harmful microorganisms. Lymph nodes may swell during infections.
* tumor (TOO-mor) is an abnormal growth of body tissue that has no known cause or physiologic purpose. A tumor may or may not be cancerous.
* radiation therapy is a treatment that uses high-energy radiation from x-rays and other sources to kill cancer cells and shrink cancerous growths.
* palliative (PAL-ee-at-iv) means to ease or relieve without curing.
* chemotherapy (KEE-mo-THER-apee) is the treatment of cancer with powerful drugs that kill cancer cells.
* stroke is a brain-damaging event usually caused by interference with blood flow to the brain. A stroke may occur when a blood vessel supplying the brain becomes clogged or bursts, depriving brain tissue of oxygen. As a result, nerve cells in the affected area of the brain, and the specific body parts they control, do not properly function.