A thin membrane of mesothelial cells, known as the peritoneum envelops many of the organs in the abdomen. Peritoneal mesothelioma is a tumor that is on this membrane. Its only known cause is exposure to asbestos, and because it can lay dormant for many years it is not detected until the tumor has begun to grow. Peritoneal mesothelioma accounts for about one-fifth of all mesothelioma cases.

The rarest form of this cancer is pericardial mesothelioma. It causes symptoms such as shortness of breath combined with severe chest pains and an irregular heart beat. It can feel like any number of heart-related conditions and may be diagnosed only after other possibilities are ruled out.

Pericardial mesothelioma is cancer of the pericardium—the thin lining that surrounds the heart. Pericardial mesothelioma is also the rarest form of mesothelioma cancer. The pericardium keeps the heart contained within the chest cavity, preventing the heart from ever–expanding as blood volume increases. The most common clinical signs of pericardial mesothelioma are:

Before the grave dangers of asbestos were known, and even for years after the dangers were known, asbestos was used in literally thousands of asbestos products that humans and animals encounter every day — particularly in building components such as ceiling and floor tiles, walls, bricks and stucco, and in automotive parts such as brakes and clutches.

One of the great tragedies of mesothelioma is that mesothelioma symptoms often mimic those of other diseases. Many people go undiagnosed, or are misdiagnosed, for some time after they first show symptoms because they are so similar to those of other diseases.

A patient with mesothelioma often demonstrates symptoms 15 to 50 years after initial exposure to asbestos. The cancer may take decades to develop in the body and symptoms do not arise until after the cancer is present. Many patients are unaware of the severity of their condition since mesothelioma symptoms typically resemble symptoms of less serious illnesses.

Malignant mesothelioma is the most serious of all asbestos-related diseases. Although uncommon, mesothelioma is no longer considered rare. Mesothelioma is a cancer that is particulary difficult for doctors to diagnose and one that does not respond well to therapy.