Mesothelioma

A malignant tumor of the mesothelium. The mesothelium is the thin lining on the surface of the body cavities and the organs that are contained within them. Most mesotheliomas begin as one or more nodules that progressively grow to form a solid coating of tumor surrounding the lung, abdominal organs, or heart. Mesothelioma most commonly occurs in the chest cavity and is associated with exposure to asbestos in up to 90% of cases. It has been shown that some asbestos fibers that are inhaled quickly work their way through the lung tissue and into the chest (pleural) cavity. Asbestos fibers that are swallowed have been shown to penetrate the wall of the intestine and appear in the abdominal (peritoneal) cavity. The risk of mesothelioma increases with the intensity and duration of exposure to asbestos. It is debatable whether or not there is any safe exposure level. Mesothelioma typically does not occur for 20 to 50 years following exposure to asbestos. Some forms of asbestos, particularly crocidolite fibers, are more likely to cause mesotheliomas. There is also evidence that mesotheliomas may be caused by other agents including radiation, viruses, and man-made mineral fibers. There is no relationship to smoking. Mesothelioma is currently difficult to treat in most cases and survival beyond two years is unusual.

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A rare neoplasm derived from the lining cells of the pleura and peritoneum which grows as a thick sheet covering the viscera, and is composed of spindle cells or fibrous tissue which may enclose glandlike spaces lined by cuboidal cells. [mesothelium + G. -oma, tumor]

- benign m. SYN: solitary fibrous tumor.

- benign m. of genital tract SYN: adenomatoid tumor.

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me·so·the·li·o·ma .mez-ə-.thē-lē-'ō-mə, .mēz-, .mēs-, .mes- n, pl -mas also -ma·ta -mət-ə a tumor derived from mesothelial tissue (as that lining the peritoneum or pleura)

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n.

a tumour of the pleura, peritoneum, or pericardium. The occurrence of pleural mesothelioma is often due to exposure to asbestos dust (see asbestosis), and workers in the asbestos industry who develop such tumours are entitled to industrial compensation. In other cases there is no history of direct exposure to asbestos at work, but the patients had been exposed to asbestos via the clothes of relatives who had had direct contact with asbestos, or they themselves had lived very close to an asbestos factory. There is no curative treatment for the disease, but moderately good results have occasionally been obtained from radical surgery for limited disease, from radiotherapy, and more recently from chemotherapy.

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meso·the·li·o·ma (mez″o-) (me″zo-the″le-oґmə) a tumor derived from mesothelial tissue (peritoneum, pleura, pericardium); both benign and malignant varieties exist. Malignant varieties are often the result of excessive exposure to asbestos.