Malignant mesothelioma is a lethal cancer that affects the lining of the lung, chest cavity, or abdominal cavity. The only known cause for mesothelioma, malignant and benign, is exposure to asbestos. It is the presence of microscopic asbestos fibers within the body that cause mesothelioma. The disease develops in the mesothelium, membrane found throughout the body that serves as a covering and protective surface for several of the body's internal organs, as well as lining for the chest cavity and the abdominal cavity. Cancer that develops in the mesothelium is called mesothelioma. Benign mesothelioma is usually a soft tumor that develops on either the membrane lining the chest cavity wall or on the abdominal cavity wall. It does not develop as a diffuse cancer, like malignant mesothelioma often does, and is relatively rare. Benign mesothelioma accounts for about 10% of all diagnosed mesothelioma cases.
Three Types of Malignant Mesothelioma
Pleural Mesothelioma develops in the section of the mesothelium that provides the outer lining of the lungs and that lines the chest cavity wall. This section of the mesothelium is called the pleura; the area between the two membranes is called the pleural space or pleural cavity. This form of the disease is by far the most common, constituting seventy percent or more of all diagnosed cases of malignant mesothelioma. The reason this form of the disease is predominant is that the asbestos fibers that cause it most often are internalized by breathing. They are tough microscopic fibers that can be inhaled unknowingly in any location where an old or torn asbestos product may release them; they are invisible and light enough to float on a cloud of dust.
Peritoneal Mesothelioma is located in the membrane that lines the wall of the abdominal cavity. This form of the disease accounts for fifteen to twenty percent of all diagnoses. It begins by thickening and inflaming the peritoneal mesothelium, or peritoneum, which often causes the development of excess fluid in the area. Pressure develops on the intestines and other nearby organs, resulting in a number of symptoms that are often read as intestinal blockage, kidney problems, or liver disease.
Pericardial Mesothelioma is the most unusual diagnosis, occurring in five percent or less of all malignant mesothelioma cases. This portion of the mesothelium forms a sac around the heart. When the disease becomes active it causes the membrane – known as the pericardium – to thicken, harden and put pressure on the heart. The result is often heart palpitations, arrhythmia, chest pain that is commonly associated with heart disease, and if the pericardium becomes too thick, heart failure.
Cell Types of Malignant Mesothelioma
Mesothelioma is also broken down into cell types; there are two distinct types of cancer cells that may be part of this malignancy. Epithelioid mesothelioma is caused by epithelial cells; about 50% to 60% of mesothelioma cancers are of this type. It tends to have a better prognosis than the other types. Sarcomatoid or fibrous cells cause 10% to 20% of malignant mesotheliomas. These cases are much more difficult to treat effectively. The third possibility is biphasic mesothelioma, which includes both types of cells. They make up about 30% to 40% of all cases.
Malignant Mesothelioma Risk
The most common cause of malignant mesothelioma is asbestos exposure. Workers in the steel, mining, plumbing, milling, insulation, and power generation industries, among hundreds of others who handle or manufacture asbestos products, are at the highest risk of developing malignant mesothelioma. Asbestos exposure in the workplace has resulted in tens of thousands of mesothelioma cases over the past half century, as asbestos was a widely used component of industrial, manufacturing and construction products.
While the risks of the disease increase depending on the frequency and intensity of asbestos exposure, there have been a number of malignant mesothelioma cases among people who have had only one or two months of exposure. One of the unusual aspects of th