Pleural mesothelioma is the most common type of mesothelioma cancer.
Pleural mesothelioma is of two kinds:
Diffuse and malignant (cancerous).
Localized and benign (non-cancerous).
Benign mesotheliomas can often be removed surgically, are generally not life-threatening, and are not usually related to asbestos exposure. All types of malignant mesothelioma, however, are very serious. Fortunately, they are rare - about two thousand people are diagnosed with mesothelioma lung cancer in the U.S. each year.
Because of the severity of it, we will write in the remainder of this section is about diffuse malignant 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 fibres, including chrysotile, amosite or crocidolite. This exposure is likely to have happened twenty or more years before the disease becomes evident, since it takes many years for the disease to "incubate." It is the most common type of mesothelioma, accounting for about 75% of all cases.
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.
The actual diagnosis usually requires obtaining a piece of tissue through a biopsy. This could be a needle biopsy, an open biopsy, or through a tube with a camera (thoracoscopy or chest scope.) If an abnormality is seen through the camera then a tissue sample can be taken at the same time, using the same tube. This is a hospital procedure that requires anesthesia, but is not usually painful. The tissue sample is tested by a pathologist.
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 cancer 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 lung cancer 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.
The tumor spreads by direct invasion of surrounding tissue. As it spreads inward it can compress the lungs. As the tumor spreads outward it can invade the chest wall and ribs, and this can be extremely painful.
Current medical science does not know exactly how and why, at a cellular level, asbestos fibers cause mesothelial cells to become abnormal (malignant or cancerous.) Thus it is not known whether only one fiber causes the mesothelioma tumor or whether it takes many fibers. It seems that asbestos fibers in the pleura can start a tumor as well as promote its growth; the tumor does not depend on any other processes for its development.
The treatment options for people with mesothelioma have improved significantly, especially for those whose cancer is diagnosed early and treated vigorously. Many people are treated with a combination of therapies.
Main types of treatment include: chemotherapy, radiation therapy, surgery and intra-operative photodynamic therapy.
There are also experimental treatments like gene therapy and immunotherapy, angiogenesis inhibitors, and clinical trials for various new treatments and combinations of treatments. Treatments that reduce pain and improve lung function, are becoming more successful (although they cannot cure mesothelioma), and pain control medications have become easier to administer.
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