Mesothelioma is a disease in which cancer cells form in the thin layer of tissue that covers the lung, heart, interior lining of the chest wall, abdominal organs, interior lining of the abdominal wall, or the testicles.
Mesothelioma is a cancer of the mesothelium. The mesothelium lines the chest and abdomen, and surrounds the organs in both the chest and abdomen. The abdomen is the part of the body that contains the liver, stomach and bowel. In the chest, the mesothelium is called the pleura, in the abdomen it is called the peritoneum. Sometimes mesothelioma can spread into the area around the heart (pericardium).
Mesotheliomas can start in four main areas in the body:
- Pleural mesotheliomas
- Peritoneal mesotheliomas
- Pericardial mesotheliomas
- Mesotheliomas of the tunica vaginalis
- start in the chest and account for three out of four mesotheliomas cases
- begin in the abdomen and account for most of the remaining cases of mesotheliomas
- start in the tissue surrounding the heart and are very rare
- start in the outer layer of the testicles and are also very rar
Incidence rates for malignant mesothelioma vary widely around the world.
For example, Japan reports an incidence of 7 people per million, while Australia reports an incidence of 40 people per million.
Most recently reported statistics include approximately 2,667 new casesof mesothelioma each year in the U.K. and about 3,000 new caseseach year in the U.S.
Overall, the highest rates of mesothelioma are reported from some countries in Europe (United Kingdom, The Netherlands, Malta, Belgium), Australia and New Zealand.
In New Zealand in 2008, almost 100 new cases were recorded. Numbers are likely to increase, due to past workplace practices which exposed people to airborne asbestos fibres. Australian information states that it may take over twenty years after exposure for any disease caused by asbestos to show up (it can take up to and over 50 years). However, most workers exposed to asbestos won’t develop mesothelioma.
Sometimes mesothelioma cancer causes fluid to accumulate in the chest or abdomen. Additional symptoms may include:
- Trouble breathing
- PAIN UNDER THE RIB CAGE
- PAIN OR SWELLING IN THE ABDOMEN
- LUMPS IN THE ABDOMEN
- UNEXPLAINED WEIGHT LOSS
The pleura are two fibrous sheets of tissue that cover the lungs and help to protect them. Doctors may call these the lining of the lungs. The term may be a bit confusing for non-medical people as they are on the outside of the lungs. The pleura are also sometimes called the pleural membranes. They are about the thickness of plastic food wrap. The inner (visceral) layer is attached to the lungs and the outer (parietal) layer lines the chest wall and diaphragm. The gap between the two pleura is called the pleural space or cavity.
The pleura produces a fluid that fills the gap. As we breathe, the fluid helps the lungs to move smoothly in the chest when they are inflating and deflating. Pleural mesothelioma causes the pleura to thicken and many tiny lumps are formed. This thickening can press on the lung or attach itself to the inside of the chest wall making it harder for the lung to expand. Fluid collects between the two layers of the pleura and presses against the lung. This is called a pleural effusion.
Most mesothelioma is caused by exposure to asbestos. Asbestos is a mineral rock made up of masses of tiny fibres. Asbestos was widely used in building materials, insulation, fire proofing, and sound absorption. When asbestos is disturbed, it sends up fibres into the air that can be easily breathed in. Once the fibres are in the lung or abdomen, the body tries to break the fibres down and remove them, leading to inflammation. Other causes of mesothelioma are not fully understood, but on rare occasions mesothelioma has been linked to exposure to radiation.
Radiation treatment treats cancer by using radiation to destroy cancer cells. Radiation can be directed to where the cancer is in your body. Treatment is carefully planned to do as little harm as possible to the rest of your body. Radiation treatment is not often used to treat peritoneal mesothelioma. For people with pleural mesothelioma, radiation treatment to small areas of the chest often helps control pain. Side effects can include tiredness, reddened and peeling skin, and loss of hair in the treatment area.