The mesothelium consists of an individual band of bedfast to cuboidal beef basic the epithelial lining of the aqueous cavities of the physique including the peritoneal, pericardial and pleural cavities. Asbestos fibers after inhalation deposited in the parenchyma of lung, results in these fibres penetrating through into the pleural membranes where the fibre can then be carried to the pleural surface, thus leading to the development of malignant mesothelial plaques. Fibres from the lungs being transported to the abdomen and associated organs via the lymphatic system. Peritoneal mesothelioma is developed by this process, it remains unresolved. Additionally, asbestos fibres may be deposited in the gut after ingestion of sputum contaminated with asbestos fibres.

It has been known that when there is contamination of pleural membranes with asbestos or other mineral fibres causes cancer (carcinogenesis). Pleural mesothelioma usually begins as discrete plaques and nodules that coalesce to produce a sheet-like neoplasm. At the lower part of the chest tumor growth usually begins. The tumor may invade the diaphragm and encase the surface of the lung and interlobar fissures. The tumor may also grow along drainage and thoracotomy tracts. As the disease progresses, it often extends into the pulmonary parenchyma, chest wall, and mediastinum. Pleural mesothelioma may extend into the esophagus, ribs, vertebra, brachial plexus, and superior vena cava.

Long thin asbestos fibers (blue asbestos, amphibole fibers) are more potent carcinogens than “feathery fibers” (chrysotile or white asbestos fibers). However, the development of mesothelioma in rats has been demonstrated following intra-pleural inoculation of phosphorylated chrysotile fibres. It has been suggested that in humans, transport of fibres to the pleura is critical to the pathogenesis of mesothelioma.

Testicular mesothelioma is extremely rare, very little is known about how it develops. Asbestos fibers once they enter the body get lodged in the spaces of the mesothelial cells causing infection leading to inflammation which further develops into mesothelioma. The fibers cause the cancerous cells to grow abnormally by dividing without restraint. After toxic asbestos fibers have become lodged between the mesothelial cells of the tunica vaginalis.

Asbestos fibers are very difficult for the body to expel and can cause some surrounding cells to mutate into cancerous cells overtime. These cancerous cells then grow and divide far more rapidly than healthy cells, leading to a thickening of the membranes and the development of tumors. The cancer growth may begin on either sub-membrane but is likely to quickly spread to the other. Additionally, tumors on the testicles may be the primary cancer in the patient – or they may be secondary to peritoneal tumors.

Prolonged exposure to asbestos is only known cause of pericardial mesothelioma as well as the other types of the disease.

The cause for pericardial mesothelioma is not well known. Just like peritoneal mesothelioma, there are 3 theories:

1) Inhaled asbestos fibers are transported through the lymphatic system to the pericardium (space between the parietal & visceral peritoneum layers).

2) Asbestos fibers entered the body through foods & drinks that asbestos workers had whilst on the job. Asbestos dust & fibers in the air is common among workplaces such as factories, shipyards & metal works.

3) Asbestos fibers, once they are broken up into smaller pieces in the lungs, are carried from the lungs into the blood stream.

When a person develops mesothelioma around the lining of the heart, it is mainly caused by the scar tissue that had been inhibited within the cavity for many years. The fibers are pumped through the heart, become lodged in the heart lining, and cause the chronic inflammation that leads to cancerous growths.

Once cells become cancerous they start to divide more rapidly. As these malignant pericardial mesothelioma cells continue to grow they lead to the thickening of the pericardial membranes, and eventually cause tumors to develop. These changes in the pericardial membrane lead to the build-up of fluid between the pericardial layers, which, combined with the thickening of the layers, puts pressure on the heart.

Even though not a definitive explanation, most important factor for development of peritoneal mesothelioma is exposure to Asbestos.

Peritoneal mesothelioma is caused,

• When asbestos fibers are ingested in water or (more rarely) food, and then migrate through the stomach or intestinal wall.
• When the asbestos fibers come in the lungs and then migrating into the peritoneum via the lymph system or the bloodstream.
• It is even possible that asbestos fibers might be present in sputum which is coughed up and then ingested.

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When asbestos fibers are ingested, they cannot be removed by the body’s immune system because of their durability. Minute fibers enter the stomach and penetrate the stomach lining. As more and more fibers penetrate this delicate organ, the cells on the exterior lining begin to mutate into cancerous mesothelioma cells. They cause chronic inflammation of cells in the lungs and develop a fibrosis that stop the peritoneum from functioning properly and protecting abdominal organs. These cells accumulate into tumors, and eventually overwhelm the peritoneum, killing off healthy stomach cells in the process. The tumors on the stomach lining grow and exert increasing pressure on surrounding organs causing agonizing pain.

Pleural Mesothelioma:

Exposure to asbestos through job related duties or in a particular environment is a primary cause of mesothelioma. In pleural mesothelioma asbestos particles are directly inhaled into lungs and pleural region. Once these fibers have entered the lungs, they work their way to the pleural membrane. Inhaling asbestos causes a build-up of fibers inside the lungs, and due to the microscopic size and sharpness of the fibers it is possible for them to penetrate the walls of the lung and enter the pleural cavity.

Pleural mesothelioma affects the lining of the lung and chest cavity known as the pleura. The pleura is made up of the parietal and visceral pleura. The parietal pleura lines the chest wall and diaphragm while the visceral pleura lines the lungs.

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Fluid between these two membranes allows asbestos particles to slip against one another as the lungs expand and contract. Once there the body finds it difficult to dislodge the asbestos particles through normal body mechanisms. As a result they remain there for a very long time. When asbestos fibers settle in the pleura, they cause inflammation which leads to development of malignant cancer.

After such a long latency period they start interfering with the mesothelial cells in the pleural region and cause changes in the pleural cells. As a result of this interference the normal functioning of the mesothelial cells is disrupted and they start growing in an uncontrolled manner. This uncontrolled growth leads to the thickening of the pleural walls and building up of fluid in the pleural area. Eventually the formation of cancerous tissues (tumors) takes place. Asbestos fibers cause changes in these pleural cells, which may cause scarring of the lungs and, eventually, the formation of tumors. When this happens, the patient feels distorting pain & shortness of breath. Also, if pleural mesothelioma develops into advanced stages, it can spread to nearby organs such as the heart, lymph nodes and abdomen.

Radiation

In the past, certain x-rays used a material called thorium doxide. It was later to have been found to cause mesothelioma. It is known that both pleural and peritoneal forms of mesothelioma have developed after exposure to radiation caused by thorium dioxide (Thorotast) which was used until the 1950s in certain X-ray machines.

Zeolite

Zeolite is a natural occurring mineral in the Turkish region, Anatoli. Zeolite is found in the soil and is very similar to asbestos. It may also cause mesothelioma.

SV40 virus

Over the past several years, some research studies have indicated a possible link between SV40 (the simian virus) and the risk of developing mesothelioma. Some studies have raised the possibility that infection with simian virus 40 (SV40) might increase the risk of developing mesothelioma. Some injectable polio vaccines given between 1955 and 1963 were contaminated with SV40. As many as 30 million people in the United States may have been exposed to the virus. Some lab studies have suggested that SV40 infection may cause mesothelioma. SV40 virus does not directly cause mesothelioma. However, it may be that SV40 may predispose a person infected with it to and increased risk of developing mesothelioma. As such it is a co-factor for the disease.