Mesothelioma means cancer of the mesothelium (-oma is a medical term for tumor or cancer). The mesothelium is the sac that lines and protects vital organs such as the heart, the lungs, and the abdominal cavity (stomach). This disease causes the cells of the lining to become abnormal and malignant. About two thirds of all mesothelioma cases develop in the pleural mesothelium or lung lining. The remaining cases, about one third, develop in the abdomen. Rarely, mesothelioma occurs in other mesothelial tissue, such as around the heart or in the reproductive organs.
Malignant pleural mesothelioma (MPM) affects over 2,000 people a year in the US, and considering the 30- to 40-year latency period between exposure and expression of the disease, there will be an estimated 300,000 cases before the year 2030. Epidemiological studies predict that approximately 250,000 Europeans will develop mesothelioma in the next few decades.
Without treatment, most patients will die from mesothelioma within 4 to 12 months from the time of diagnosis. Patients generally die as a result of respiratory failure or pneumonia. Small bowel obstruction, resulting from direct extension of tumor through the diaphragm, develops in about one-third of patients. About 10% die of cardiac complications when the tumor invades the pericardium and heart. Three subtypes of mesothelioma have been identified according to microscopic appearance; these are epithelial, sarcomatoid, and mixed types. A number of studies have demonstrated that the epithelial variant is associated with the best prognosis. Other favorable prognostic variables include younger age, good performance status, early stage disease, and lack of chest pain at diagnosis.
The increased incidence of mesothelioma has been closely linked to the rise of the asbestos industry and the use of asbestos in fireproofing and insulation. Between 50% and 80% of patients diagnosed with MPM are aware of exposure to asbestos at some point in their lives. Men are typically affected more, due to the common presence of asbestos in industrial settings. The increasing incidence suggests either that the benefits of legislation to reduce asbestos exposure in the workplace have not yet taken effect, or that asbestos exposure during the 1960's was more widespread than previously believed. In addition, some researchers have implicated exposure to the SV-40 virus, which is known to have contaminated some polio vaccines, as potentially related to this malignancy, but this has not been proven.
The absence of asbestos exposure in a significant percentage of mesothelioma patients is used by some experts to argue for a genetic predisposition. The fact that only about 5% of South African asbestos mine workers developed mesothelioma suggests that other environmental or genetic factors are involved. Another associated risk factor is radiation. Radiation-induced malignant mesothelioma appears to have the same prognosis as asbestos-related mesothelioma.
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This page was last modified on 12/5/2011