Mesothelioma, or malignant mesothelioma, is a rare kind of cancer. It starts in the mesothelium, a thin lining that protects the outer surface of some organs, including the lungs, stomach/abdominal space and chest wall. The mesothelium also makes fluid that helps the organs move against each other during certain processes, such as breathing. The mesothelium has different names for different body parts:

  • The lining in the chest is the pleura.
  • The lining in the abdomen is the peritoneum.

Mesothelioma can start in any of these linings. It’s most common in the chest, where it’s called pleural mesothelioma. The second most common site is the abdomen, where it’s called peritoneal mesothelioma.