Malignant Mesothelioma is a type of cancer that is most commonly associated with asbestos exposure. In fact the only known cause for the pathogenesis of malignant mesothelioma is asbestos. This cancer affects the areas of the human body where mesothelial cells are found.
Pleural Mesothelioma comprises the majority of malignant mesothelioma cases. This is the type of malignant mesothelioma that affects the pleura, which is the lining of the lungs. Approximately 70% of all cases of malignant mesothelioma occur in the pleura. As asbestos fibers that are sloughed off of asbestos containing products get inhaled by humans, these then get lodged in the lining of the lungs. The human body has no capability of physiologically eliminating such fibers. In time, these accumulated fibers will find they way into the mesothelial cells of the pleura. These asbestos fibers are considered foreign bodies by the body. Thus, their presence causes reactive inflammatory processes to occur, which is manifested by pleural thickening, plaque formations, vasculitis and even effusions. As the disease progresses, the thickening of the parietal and visceral pleura causes the narrowing of the pleural space. In time, the two leaves of the pleura rub against each other. These processes are manifested as dyspnea, rales and even chest pain or discomfort, fatigue, and weight loss in the patient. Continued hypertrophy of mesothelial cells due to the assaultive presence of these fibers will then result in the formation of tumors. On average, it takes about 40 years from exposure to these fibers to the manifestation of first symptoms.
Peritoneal mesothelioma comprises about 20 to 25% of all malignant mesothelioma cases. This is the type of mesothelioma that affects the mesothelial cells of peritoneum. As asbestos fibers come into contact with the mesothelial cells, they effect changes that cause the cells to multiply without restraint, and to thicken. Ascites also occurs. Together, these cause pressure buildup in the abdominal cavity. This pressure affects the other internal organs and causes them to deteriorate. Intestinal obstruction often ensues. Thromboses of intestinal veins as well as hypoglycemia, and anemia are common initial symptoms. Lesions can vary from single tumors, small diffuse tumors, or calcified nodules.
Pericardial mesothelioma comprises about 5% of all cases of malignant mesothelioma. This is the least common type of mesothelioma. With pericardial mesothelioma, malignant tumors are found on the pericardium, the fibrous tissue sac surrounding the heart. It is speculated that the way asbestos fibers travel to the heart is through the lymphatic system or through the cardiovascular patient. As with the other types of mesothelioma, asbestos fibers cause the cells of the pericardium to thicken. This thickening affects pressure on the chambers of the heart. This in turn causes severe shortness of breath, chest pain, as well as thromboses in the veins. In time, the thickening also causes the mesothelial cells to undergo unrestricted division and growth, leading to the formation of tumors. As with the other types, the excess pressure buildup from the tumor growth puts pressure on the heart contributing to congestive heart failure.