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Mesothelioma is a malignant cancer of either the pleura (the membrane that separates the rib cage from the outer surface of the lungs) or the peritoneum (the membrane that surrounds the abdominal cavity). Mesothelioma’s principal cause is exposure to asbestos.

The Difference Between Mesothelioma and Other Asbestos-Related Diseases

Historically the asbestos-related diseases asbestosis, pleural scarring and lung cancer, have been the basis of most asbestos personal injury litigation in the United States. These diseases generally occur in “occupational” doses of exposure. In other words, people who were employed in shipbuilding, construction trades, or worked in factories that made asbestos-containing products.

The majority of mesothelioma diagnoses are caused by asbestos exposure. Besides the severity of the disease, the difference between mesothelioma and the other asbestos-related diseases is that people can get it with very little exposure. This means it’s occurring at an increasing rate among people whose only exposure to asbestos was light or intermittent — the person may not be aware they were ever exposed--and, workers with higher exposure contract mesothelioma at a rate many times that of general population.

The next wave of mesothelioma victims is people whose only exposure to asbestos may have been to work or live in a building with previously installed asbestos fireproofing or insulation present. These cases can be difficult to compensate because it is much tougher to establish the identity of the asbestos product to which the person was exposed. However, in many cases it can be done if the proper effort is put into the investigation.

Pleural plaques

The lining around the lungs and diaphragm is known as the pleura. Pleural plaques are thick, hard patches found on the pleura. As pleural plaques are neither life-threatening nor bothersome to the patient, they are typically fine left untreated.

Pleural plaques are associated with asbestos exposure. Asbestos fibers are inhaled and become lodged in the pleura. The size and shape of the fibers make it difficult for the immune system to destroy the fibers or escort them out of the body, so the surrounding membrane thickens and hardens. Researchers speculate that thickening is part of the immune response to the presence of fibers in the lining.

Pleural plaques are typically found 20-40 years after asbestos exposure and they can become larger and harder (by calcification) over time. They are almost always found on the parietal pleura – the outer lining that surrounds the lung. Usually, a patient has an x-ray for another condition, and pleural plaques appear on the x-ray as masses.

Those with pleural plaques have an increased risk of developing lung cancers. The plaques themselves do not lead to cancer; however, they do indicate asbestos exposure, which carries its own cancer risk. Your doctor will likely put you on a screening schedule based on several factors such as how long ago you were exposed to asbestos and your estimated exposure level.


Asbestosis is the formation of scar tissue in the lungs. Symptoms include shortness of breath, coughing, chest pain, and fatigue with physical activity. It can cause high blood pressure in the lungs (pulmonary hypertension), heart problems and other lung damage. As with all asbestos-related disease, it results from inhaled asbestos fibers being lodged in the lining of the lung.

Inhaled air passes through a series of filters, such as nose hairs and mucous membranes, to minimize the amount of foreign bodies and chemicals that reach the lungs. At the last stop before oxygen reaches the rest of the body, the air sacs where oxygen-carbon dioxide exchange occurs (alveoli), house their own immune cells to destroy the last bit of dust and chemicals that passed through.

Because of the size and shape of asbestos fibers, these immune cells cannot break down or dislodge the fibers from the lining. They get stuck in the lining of the lung, often indefinitely. The immune cells repeatedly try to destroy the fibers with a harsh chemical that damages the alveoli.

This process causes the patient to feel short of breath in two ways. First, damaged alveoli mean that fewer alveoli are available to exchange oxygen and carbon dioxide, so more breathing may be required to maintain proper oxygen and carbon dioxide levels. Second, scar tissue may develop around the damaged alveoli. Accumulation of scar tissue stiffens the lung, requiring more energy to breathe.

Not everyone develops asbestosis. Genetics seem to play a role in the immune response to asbestos fibers.

With time, more and more lung tissue becomes scarred, so asbestosis can become quite painful in advanced stages. Most commonly, though, asbestosis causes a general shortness of breath. The good news is, asbestosis is not terminal in and of itself. Asbestosis scarring does not turn into cancer, but it does indicate asbestos exposure, which is associated with increased risk of lung cancers. Your doctor will probably put your on a cancer screening schedule since asbestosis is a certain indicator of asbestos exposure. Remember, not everyone who suffers from asbestosis will develop a terminal disease.

Asbestosis is a relatively common breathing ailment among asbestos-exposed individuals, and is compensable by the Workers’ Compensation Board and by Veterans’ Affairs in some cases.

Small-cell Lung Cancer

Small cell lung cancers represent 10-15% of lung cancers. There are two types of small cell lung cancers: small cell carcinoma (also called oat cell cancer), and combined small cell carcinoma. The distinction has to do with the cells affected and the way the cancer spreads. Small-cell lung cancers may be referred to as non-squamous, which means that the tumors did not originate in the thin, flat epidermoid cells that resemble fish scales.

Small cell lung cancers are very rare in patients who have never smoked. Symptoms include chest pain, cough, loss of appetite, shortness of breath, bloody sputum, unexplained weight loss and wheezing.

Typically, it develops in the bronchi in the center of the chest. Because it spreads so quickly and symptoms are not bothersome until it has spread, small-cell lung cancers are often life-limiting. It is first seen by chest x-ray or CT scan, and confirmed by needle biopsy (testing a sample of tissue). Depending on several factors such as the degree to which it has spread and the organs affected, treatment usually includes some combination of surgery and radiation or chemotherapy.

Peritoneal Mesothelioma

Peritoneal mesothelioma is a cancer of the peritoneum, or the abdominal lining. Most mesothelioma cases are pleural - fewer than 30% of mesothelioma cases are peritoneal. Peritoneal mesothelioma is caused by the ingestion of fibers that work their way into the peritoneum, or the inhalation of fibers that the lymph system transports to the peritoneum.

A healthy abdominal lining produces fluid that keeps organs from rubbing directly against each other. Cancer can cause the lining to secrete too much of this fluid, which crowds organs and results in discomfort, abdominal swelling, weight gain, digestive problems, and even swelling of feet and ankles.

Other symptoms unrelated to fluid buildup are abdominal pain and swelling associated with tumor growth, weight loss from compression by tumors, bowel obstruction, anemia and fever.

Peritoneal mesothelioma is difficult to diagnose and is often missed or mistaken for another condition. If the patient sees a doctor for fluid buildup, a doctor may drain the fluid and test it under the microscope. Or, tumors can be seen on x-ray, CT, or MRI. Either way, a needle or surgical biopsy is the only way to confirm the diagnosis.

Depending on the specific test you need and other factors, it may take time to schedule a test. It is important to call your doctor as soon as you suspect you have been exposed to asbestos, or if you start feeling symptoms, no matter how mild they are.

Pleural Mesothelioma

Pleural mesothelioma, cancer of the lining of the diaphragm, represents over 70% of mesotheliomas. Symptoms include shortness of breath, painful breathing, painful coughing, unexplained weight loss, dry cough, pleural effusion (fluid buildup), and lumps under the skin of the chest.

In the case of pleural effusion, a sample of the fluid may be taken and tested under a microscope. If the fluid is clear (transudate), something is disrupting the balance between the production and the absorption of fluid. If the fluid is cloudy (exudates), cells and proteins are present, indicating a diseased pleura. This is common to mesothelioma patients.

When symptoms other than fluid-related symptoms cause the doctor visit, CT or MRI may indicate the presence of mesothelioma. Either way, needle biopsy confirms the diagnosis. As with peritoneal mesothelioma, it may take time to schedule a test, so call your doctor as soon as you suspect you have been exposed to asbestos, or if you start feeling even mild symptoms.

Also as with peritoneal mesothelioma, the cancer has usually spread by the time of diagnosis, so some combination of surgery and radiation or chemotherapy may be prescribed depending on the stage at diagnosis and affected organs (see Treatment Options).

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