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What is Malignant Mesothelioma?

Most cancers find their names in the part of the body where the cancer first starts. Malignant Mesothelioma originates in tissue that surrounds different organs inside the body. This tissue, called mesothelium, protects the lungs, heart and stomach by making a special fluid that allows the organs to move. This fluid makes it easier for the lungs to move when breathing, the heart to move when beating, and the stomach to move when digesting. Tumors can start in any of these places. These tumors can be benign (non-cancerous) or malignant (cancerous). The information that follows concerns only malignant tumors.

The National Cancer Institute (NCI) identifies malignant mesothelioma as a rare form of cancer. Doctors only diagnose two to three thousand cases per year in the United States, with men three to five times more than women likely to suffer from Malignant Mesothelioma. Although rare, the incidents of Malignant Mesothelioma appear to be increasing.

The NCI further describes Malignant Mesothelioma as "a disease in which cancer (malignant) cells are found in the sac lining the chest, the lining of the abdominal cavity or the lining around the heart." Doctors have identified three types of malignant mesothelioma. refers to a cancer of the lining of the lung (pleura). affects the lining of the abdominal cavity (peritoneum). While pericardial mesothelioma is a cancer of the lining surrounding the heart (pericardium). About three-fourths of mesotheliomas start in the chest cavity. Another 10 to 20 percent begin in the abdomen, while those starting around the heart are very rare.

Three main sub-types of mesotheliomas exist. Sub-types (or cell types) of mesothelioma include the epithelioid type. This type accounts for 50 to 70 percent of all mesotheliomas and has the best outlook for responding to treatment. The other two types, mixed/biphasic and sarcomatoid, are less common. In general, the treatments for all three are the same.

Although rare, Malignant Mesothelioma represents a serious health threat to those diagnosed. Because it often becomes advanced before symptoms appear the outlook is not as good as it is for cancers that doctors find earlier. About half of the patients whose doctors find and treated the cancer early will survive two years or more. The average survival time for all stages of Malignant Mesothelioma is about one year.

What Causes Malignant Mesothelioma?

The main risk factor for mesothelioma is contact with asbestos. A person breathes in asbestos fibers, which then travel to the ends of the small air passages, and reach the lining of the lungs. There they can damage the mesothelial cells or the lining of the lung cells. If swallowed, these fibers can also reach the lining of the abdominal cavity where they play a part in causing a cancer called peritoneal mesothelioma.
A latency period of 20 to 50 years or more between initial exposure and development of mesothelioma exists. While researchers document the average latency period as between 35 and 40 years, they have documented rare instances when the period was less than 20 years.

The chances of suffering from mesothelioma rise with the intensity and duration of exposure to asbestos; however, numerous cases of mesothelioma occurred among people with very little occupational exposure or household exposure. Cases exist of people getting mesothelioma 30 or 40 years after a summer job working construction, and housewives or children being exposed from work clothing.

Prior to the mid-1970's, most insulation materials contained asbestos. Many other construction materials also contained asbestos, including, pipe insulation, boiler insulation, fireproofing spray, firebrick and gunnite (used for internal insulation of furnaces and boilers), roof, floor and ceiling tiles, transite siding, and brakes and clutches.

Because occupational exposure to asbestos often accounts for the most prolonged and intense exposure to asbestos, many people who worked with asbestos now suffer from mesothelioma. Among those trades in which a risk of asbestos exposure existed are insulators who installed asbestos insulation, boilermakers who constructed massive boilers filled with asbestos insulation, plumbers, pipefitters and steamfitters who fitted and welded pipes together and often worked in small unventilated compartments in ships where large quantities of insulation were used, plasterers who worked with fireproofing spray on steel beams, shipyard workers, electricians and mechanics, bricklayers, millwrights, carpenters, steel workers, refinery and industrial workers, and maintenance workers.