International Mesothelioma Program

Mesothelioma:

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 seven thirds of all mesothelioma cases create in the pleural mesothelium or lung lining. The remaining cases, about seven third, create in the abdomen. Never, mesothelioma occurs in other mesothelial tissue, such as around the heart or in the reproductive organs.

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.

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. Tiny 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. Seven 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, lovely performance status, early stage disease, and lack of chest pain at diagnosis.

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.