Mesothelioma Causes

Asbestos

The major known cause of mesothelioma is exposure to asbestos. A known history of asbestos exposure is present in 70-80% of all cases of mesothelioma. Asbestos likely causes cancer by physically irritating the cells. When asbestos fibers are breathed in, they reach the ends of the small airways and penetrate into the pleura (lining of the lung). These fibers may then injure mesothelial cells of the pleura and eventually cause mesothelioma.

The risk of developing mesothelioma rises with the quantity of asbestos exposure. However, genetic factors also play a role in determining who develops the condition. This is probably the reason why all people exposed to high levels of asbestos do not develop mesothelioma.

Smoking

Although smoking has not been associated with the development of mesothelioma, the combination of smoking and asbestos exposure significantly increases a person's risk of developing pleural mesothelioma.

Other Causes

Mesothelioma also has been linked to the following:

* Radiation: Mesothelioma has been reported to occur in few people following exposure to therapeutic radiation using thorium dioxide (Thorotrast).


* Zeolite: Zeolite is a silicate mineral (chemically related to asbestos) commonly found in the soil of the Anatoli region of Turkey. A few cases of mesothelioma reported from this region may have been caused by zeolite.


* Simian virus 40 (SV40): The role of SV40 in the development of mesothelioma has also been suggested. This virus has been identified in human mesothelioma cells. In studies conducted in animals, it has been shown to induce the development of mesothelioma.

What is Mesothelioma?

Mesothelioma is a form of cancer that is almost always caused by previous exposure to asbestos. In this disease, malignant cells develop in the mesothelium, a protective lining that covers most of the body's internal organs. Its most common site is the pleura (outer lining of the lungs and chest cavity), but it may also occur in the peritoneum (the lining of the abdominal cavity) or the pericardium (a sac that surrounds the heart).

Most people who develop mesothelioma have worked on jobs where they inhaled asbestos particles, or have been exposed to asbestos dust and fibre in other ways, such as by washing the clothes of a family member who worked with asbestos, or by home renovation using asbestos cement products. Unlike lung cancer, there is no association between mesothelioma and smoking.

Symptoms of mesothelioma may not appear until 20 to 50 years after exposure to asbestos. Shortness of breath, cough, and pain in the chest due to an accumulation of fluid in the pleural space are often symptoms of pleural mesothelioma.

Symptoms of peritoneal mesothelioma include weight loss and cachexia, abdominal swelling and pain due to ascites (a buildup of fluid in the abdominal cavity). Other symptoms of peritoneal mesothelioma may include bowel obstruction, blood clotting abnormalities, anemia, and fever. If the cancer has spread beyond the mesothelium to other parts of the body, symptoms may include pain, trouble swallowing, or swelling of the neck or face.

These symptoms may be caused by mesothelioma or by other, less serious conditions.

Mesothelioma that affects the pleura can cause these signs and symptoms:

* chest wall pain
* pleural effusion, or fluid surrounding the lung
* shortness of breath
* fatigue or anemia
* wheezing, hoarseness, or cough
* blood in the sputum (fluid) coughed up

In severe cases, the person may have many tumor masses. The individual may develop a pneumothorax, or collapse of the lung. The disease may metastasize, or spread, to other parts of the body.

Tumors that affect the abdominal cavity often do not cause symptoms until they are at a late stage. Symptoms include:

* abdominal pain
* ascites, or an abnormal buildup of fluid in the abdomen
* a mass in the abdomen
* problems with bowel function
* weight loss

In severe cases of the disease, the following signs and symptoms may be present:

* blood clots in the veins, which may cause thrombophlebitis
* disseminated intravascular coagulation, a disorder causing severe bleeding in many body organs
* jaundice, or yellowing of the eyes and skin
* low blood sugar level
* pleural effusion
* pulmonary emboli, or blood clots in the arteries of the lungs
* severe ascites

A mesothelioma does not usually spread to the bone, brain, or adrenal glands. Pleural tumors are usually found only on one side of the lungs.

(source:en.wikipedia.org/wiki/Mesothelioma)