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Types of Mesothelioma
What are the types of mesothelioma?
There are two main types of mesothelioma, peritoneal mesothelioma and pleural mesothelioma, though are several less frequent varieties.
Peritoneal mesothelioma
Peritoneal mesothelioma is found in the abdomen in a thin membrane called the peritoneum. Symptoms include abdominal swelling, loss of appetite, and weakness. The only known cause to this disease is exposure to asbestos. Due to the latency effect of this cancer, this exposure is likely to have taken place 20 or more years ago. This type of mesothelioma is the less common and is found in less than 30% of all mesothelioma cases.
The growing tumor can put increasing pressure on the abdomen, leading to bowel obstruction and distention. If the tumor presses upward, it can impair breathing. If the tumor pushes against areas with many nerve fibers, and the bowel distends, the amount of pain can increase.
There are at least two explanations for how asbestos fibers can get into the peritoneum. The first is that fibers caught by the mucus of the trachea and bronchi end up being swallowed. Some of them lodge in the intestinal tract and from there they can move through the intestinal wall into the peritoneum. The second explanation is that fibers that lodge in the lungs can move into the lymphatic system and be transported to the peritoneum.
At this time there no known cure for peritoneal mesothelioma. The prognosis depends on various factors, including the size and stage of the tumor, its extent, the cell type, and whether or not the tumor responds to treatment.
Pleural Mesothelioma
Pleural mesothelioma is a cancer of the cells that make up the pleura or lining around the outside of the lungs and inside of the ribs. Its only known cause in the U.S. is previous exposure to asbestos fibers, including chrysotile, amosite or crocidolite. Exposure to these fibers within ten years of a diagnosis of this type of cancer can be considered as a likely contributing factor in the disease process. It is the most common type of mesothelioma, accounting for about 75% of all cases.
Mesothelioma is sometimes diagnosed by coincidence, before there are any symptoms. For instance, tumors have been discovered through routine chest x-rays. However, when symptoms occur, they may include shortness of breath, weakness, weight loss, loss of appetite, chest pains, lower back pains, persistent coughing, difficulty in swallowing, alone or in combination. An initial medical examination often shows a pleural effusion, which means an accumulation of fluid in the pleural space - the area between the lungs and the chest wall.
The first step in detecting pleural mesothelioma is, typically, a chest x-ray or CT scan. This is often followed by a bronchoscopy, using a viewing scope to look inside the lungs.
Fluid build-up from the pleural effusion can generally be seen on a chest x-ray and heard during a physical examination, but a firm diagnosis of mesothelioma can only be made through a biopsy and pathological testing. This is important because there are also benign pleural effusions and other tumors that have a similar appearance to mesothelioma. Diagnosing mesothelioma can be quite difficult; it requires special lab stains, and much experience in understanding them.
The spread of the tumor over the pleura causes pleural thickening. This can reduce the flexibility of the pleura and encase the lungs in an increasingly restrictive girdle. With the lungs restricted, they get smaller and less functional, and breathing becomes more difficult. At first a person with mesothelioma may be breathless only when he or she exercises, but as lung function drops, he or she can become short of breath even while resting.
What part of the body does mesothelioma affect?
Mesothelioma affects the mesothelium, tissue formed by specialized cells lining the chest, abdominal cavities and outer surface of most internal organs. The mesothelium produces a lubricating fluid that helps organs by enabling them to move.
How is mesothelioma diagnosed?
Diagnosing mesothelioma is often difficult, because the symptoms are similar to those of a number of other conditions. Diagnosis begins with a review of the patient's medical history, including any history of asbestos exposure. A complete physical examination may be performed, including x-rays of the chest or abdomen and lung function tests. A CT (or CAT) scan or an MRI may also be useful. A CT scan is a series of detailed pictures of areas inside the body created by a computer linked to an x-ray machine. In an MRI, a powerful magnet linked to a computer is used to make detailed pictures of areas inside the body. These pictures are viewed on a monitor and can also be printed.
Types of mesothelioma - peritoneal, pleural
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