The mesothelium is a membrane that covers and protects most of the internal organs of the body. It is composed of two layers of cells: One layer immediately surrounds the organ; the other forms a sac around it. The mesothelium produces a lubricating fluid that is released between these layers, allowing moving organs (such as the beating heart and the expanding and contracting lungs) to glide easily against adjacent structures.
Mesothelioma (cancer of the mesothelium) is a disease in which cells of the mesothelium become abnormal and divide without control or order. They can invade and damage nearby tissues and organs. Mesothelioma cancer is almost always caused by previous exposure to asbestos. Most people who develop mesothelioma cancer have worked on jobs where they inhaled asbestos particles, or have been exposed to asbestos dust and fibre in other ways, such as by washing the clothes of a family member who worked with asbestos, or by home renovation using asbestos cement products. Unlike lung cancer, there is no association between mesothelioma and smoking.
Mesotheliomas are uncommon cancers, although they are becoming more frequent. Currently, about 1800 people in the UK are diagnosed with mesothelioma cancer each year. Mesothelioma of the lining of the lungs (pleural mesothelioma) is much more common than mesothelioma in the peritoneum. For every person with peritoneal mesothelioma there will be about 12 people who have pleural mesothelioma.
