A mesothelioma is a tumor of the pleura. The pleura are the membranes which cover the lungs. Mesotheliomas have also been shown to occur in lab animals exposed to ionizing radiation and natural and artificial fibrous material. The asbestos fiber is a very long, thin fiber that can get deep into the lungs and penetrate the lung's walls, avoiding the lung's defenses against foreign particles. Picture of asbestos fibers in the lung .
Mesotheliomas are rare.
It is estimated that 2000 deaths occur per year from mesothelioma associated with asbestos exposure and that 4000-6000 deaths are from lung cancer associated with asbestos. It occurs more frequently in men over 65 with a history of asbestos exposure. It takes about 20-45 years after the initial asbestos exposure for mesotheliomas to develop. It can take anywhere from 20 to 45 years after exposure to asbestos for symptoms to appear. Symptoms arising from mesotheliomas usually come on gradually.