Mesothelial cells are a layer of specialized cells that line the body cavities, including the pleura (lining of the lung), peritoneum (lining of the abdominal cavity), and pericardium (lining of the heart). The tissue formed by these cells is called mesothelium.
The mesothelium contains both an outer and an inner layer. The inner layer surrounds the organs themselves, while the outer layer lines the body cavities The mesothelial cells themselves produce and secrete a small amount of lubricating fluid between the two layers that permits the organs to move smoothly against adjacent organs and structures.
Like other cells of the body, mesothelial cells can also grow abnormally, leading to the development of tumors. The tumors of the mesothelial cells can be benign (noncancerous) or malignant (cancerous). A malignant tumor of the mesothelium is called a malignant mesothelioma. Because most mesothelial tumors are cancerous, malignant mesothelioma is often simply referred to as mesothelioma. This article focuses on mesothelioma of the lining of the lungs (pleural mesothelioma).
The main risk factor for developing pleural mesothelioma is exposure to asbestos. Asbestos is a mineral that occurs naturally as strong, flexible fibers that can be separated into thin threads and woven. Asbestos has been widely used in many industrial products, including cement, brake linings, roof shingles, flooring products, textiles, and insulation. If tiny asbestos particles float in the air, especially during the manufacturing process, they may be inhaled or swallowed.
Prior to the 1970s, enormous amounts of asbestos were used in commercial construction and shipbuilding. After the health risks of asbestos became known, production of asbestos slowed drastically in the 1970s. Governmental restrictions were placed on its use, and alternative materials became available. Despite these changes, asbestos continues to be used.
Occupations that deal with asbestos and typically associated with the onset of mesothelioma later in life include asbestos production, insulation work, heating trades, shipyard work, and construction.
The period between asbestos exposure and the development of mesothelioma is generally 35-40 years. Usually, people who develop mesothelioma have been exposed to asbestos for a prolonged period of time; however, some people with only brief exposures have also developed mesothelioma. On the other hand, not all workers who are heavily exposed develop mesothelioma.
Mesothelioma can also occur in family members and other people living with asbestos workers. It may be a result of exposure to asbestos dust brought home on the clothing and hair of asbestos workers.
In some people with mesothelioma, no specific asbestos exposure can be found. Frequently, such people have worked in a job where the exposure was not recognized. Nevertheless, mesothelioma without asbestos exposure does occur.
Winston W Tan, MD
Shehnaz Shaikh, MD