what is mesothelioma

Mesothelioma is a cancer of the smooth lining of the chest, lungs, heart, and abdomen. This skin layer is made up of mesothelial cells, hence the name mesothelioma. Mesothelioma is a diffuse but solid tumor that begins as a result of insult to the tissues caused by asbestos particles. These have penetrated into the pleural cavity of the chest or into the abdomen. Mesothelioma is either called pleural mesothelioma or peritoneal mesothelioma based on where it appears.

Because it occurs in such a small number of patients mesothelioma is often referred to as an orphan disease. Numbers of newly affected individuals in the United States have been reported to be between 2,500 and 3,000 every year. A steady rise in cases is reported in North America, Europe, Australia, and Asia.

In its early stages mesothelioma is difficult to detect as it may start with a thickening of the pleural rind, or fluid which can be associated with many other conditions. This rind is normally thin and smooth in the non diseased state. In time it begins to demonstrate progression forming a more pronounced irregular rind and nodules which coalesce into a crust that compresses and invades into adjacent structures compromising lung and cardiac function. In the abdominal cavity it can invade into the liver and bowel rendering the patient inoperable. Peritoneal mesothelioma it is often found coating the omentum described sometimes as a salt like sand like particles too numerous to count and impossible to remove without sacrificing the entire omentum. Involvement of the ovaries and fallopian tubes is not uncommon in women and often mesothelioma is confused with ovarian cancer. Once vital organs are involved or disease identified outside of the operative field surgery is no longer an option and patients are referred to chemotherapy or clinical trials.

Figure E: Right Pleural Epithelial Mesothelioma on chest wall and lung. Photo courtesy K. Brauch

For the vast majority of patients, as the tumor mass grows, once subtle symptoms will give way to weight loss, cough, respiratory infections, fatigue, shortness of breath, digestive and bowel problems and pain in the chest or abdomen, depending upon whether it is pleural or peritoneal. It may begin to weep fluid into the intracavitary space. In the chest cavity this is called an effusion and it fills the space where the lobes of the lung reside, next to the lining of the chest cavity, and often spreads into the area surrounding the heart creating symptoms similar to those observed in congestive heart failure. In peritoneal patients it is called ascites and it fills the abdomen bathing the visceral organs with this malignant fluid.

Mesothelioma, more precisely malignant mesothelioma, is a rare form of cancer that develops from the protective lining that covers many of the body's internal organs, the mesothelium. It is usually caused by exposure to asbestos.
Its most common site is the pleura (outer lining of the lungs and internal chest wall), but it may also occur in the peritoneum (the lining of the abdominal cavity), the heart,the pericardium (a sac that surrounds the heart) or tunica vaginalis.
Most people who develop mesothelioma have worked on jobs where they inhaled asbestos particles, or they have been exposed to asbestos dust and fiber in other ways. It has also been suggested that washing the clothes of a family member who worked with asbestos can put a person at risk for developing mesothelioma.[3] Unlike lung cancer, there is no association between mesothelioma and smoking, but smoking greatly increases the risk of other asbestos-induced cancers.[4] Compensation via asbestos funds or lawsuits is an important issue in mesothelioma (see asbestos and the law).
The symptoms of mesothelioma include shortness of breath due to pleural effusion (fluid between the lung and the chest wall) or chest wall pain, and general symptoms such as weight loss. The diagnosis may be suspected with chest X-ray and CT scan, and is confirmed with a biopsy (tissue sample) and microscopic examination. A thoracoscopy (inserting a tube with a camera into the chest) can be used to take biopsies. It allows the introduction of substances such as talc to obliterate the pleural space (called pleurodesis), which prevents more fluid from accumulating and pressing on the lung. Despite treatment with chemotherapy, radiation therapy or sometimes surgery, the disease carries a poor prognosis. Research about screening tests for the early detection of mesothelioma is ongoing.