Mesothelioma stands for tumor of middle lining tissues. It is an unusual and rare type of lung cancer that arises from the cells that form a membrane that lines with the abdominal cavity of the body (also known as peritoneal membrane or peritoneum).
The abdominal cavity preserves the body's intestines while the pleural membrane (pleura) preserves the heart and lungs of the body. With Mesothelioma, these cells that store the pleura and the abdominal cavity will begin to grow beyond control and almost burst, thus forming "malignant cells." Note the meaning of "malignant" on Dictionary.com is "Cancerous or deadly or destructive." When the cells around the heart become malignant, this means the patient is more likely to develop
Mesothelioma.
By the way, malignant cells can also develop around the linings of the heart, also known as the Pericardium. See the images of both the Pericardium and the Pleura below to get a visual picture of the process. Malignant cells that develop around the Pleura or the lungs lead to shortness of breath for the patient, because of the thickening of the lining membrane. As the lining membrane thickens, the airways become blocked and the patient has trouble inhaling air in and out of his body. Find the picture of the airways around the Pleura and the lungs below. If malignant cells are developed around the abdominal cavity, this could result in abdominal swelling as the lining membranes of the gut thicken and get fat. This could also result in accumulation of large amounts of fluid in the abdomen.
Accumulation of large amounts of fluid in the abdomen is also known as Ascites.
Source: Wikipedia