The tissue that lines your lungs, stomach, heart and other organs is called mesothelium. Mesothelioma is cancer of that tissue. It is a rare but serious type of cancer. It usually starts in the lungs, but can also start in the abdomen or other organs. Most people who develop mesothelioma have worked on jobs where they inhaled asbestos particles. It can take a long time - 30 to 50 years - between being around asbestos and getting the disease. Treatment includes surgery, radiation, chemotherapy or all three.