The human body has four basic types of tissue: epithelial cells, connective cells, muscle cells, and nerve cells. Muscle and nerve cells are familiar to most people – we all know what our muscles do and what our brains and spinal cord and nerves do. Connective cells are a bit more esoteric – the connective tissue is material like cartilage and ligaments that serves as a kind of glue holding our body together. Epithelial cells are the sheaths and mucous membranes found throughout the body – our outer layer of skin is composed of epithelial cells, as is the lining of our stomachs, among many other parts of the body.
The mesothelium is made up of a single layer of large, flat epithelial cells. That layer wraps the thoracic cavity (the area holding your lungs), the abdominal cavity (where your stomach and intestines are) and your pericardium (the area around your heart). Mesothelioma is a cancer affecting this layer of cells, and is almost always caused by exposure to asbestos fibers. Mesothelioma causes the mesothelium to thicken as tumors develop, reducing its ability to expand and making breathing difficulty, and also causing pain. Nearly all mesothelioma is thought to be caused by asbestos; however, some researchers believe that scarring of the mesothelium from other causes, chronic inflammation, other carcinogenic compounds or chemicals, emphysema, or even viruses may cause some cases of mesothelioma. All researchers agree, however, that asbestos definitely is one of the primary causes.
There are different types of mesothelioma - Pleural mesothelioma, Peritoneal mesothelioma, and Pericardial mesothelioma. Mesothelioma can affect the peritoneal mesothelium (around the stomach and intestines), the pleural mesothelium around the lungs, or the pericardial mesothelium around the heart. Most cases of mesothelioma begin in the lower part of the lungs, probably because gravity causes more inhaled asbestos fibers to accumulate there. There is a localized and benign (non-metastasizing) form of mesothelioma, thought to be unrelated to asbestos exposure, which can be treated with surgical removal of the tumors. Other forms of mesothelioma are known as malignant mesothelioma, and in those cases the prognosis is not optimistic.
Unfortunately, once a mesothelioma diagnosis is made, there are no treatments for advanced mesothelioma that have been shown to have positive effect. It should be noted that every case of cancer, including mesothelioma, is unique. For example, the noted biology writer Stephen Jay Gould survived twenty years with peritoneal mesothelioma, and in fact died of an unrelated cancer. However, such cases are the exception; the general prognosis for mesothelioma patients is death within 6 to 12 months of their initial diagnosis. (In part this is because mesothelioma is difficult to diagnose, and many patients do have the disease for years before succumbing.)
Research is ongoing, however, and with new cancer medicines coming onto the market every year, there is always the possibility that new mesothelioma treatments will reduce the mortality of this deadly disease.