Research by Mesothelioma Meme – What is Mesothelioma?
Mesothelioma starts in cells of the mesothelium. A cancerous tumor is a group of cancer cells that can grow into and destroy nearby tissues. It can also spread (metastasize) to other parts of the body.
The mesothelium is a membrane that covers and protects most of your internal organs. It is made up of 2 layers. The inner layer wraps around different organs, including the lungs, heart and stomach. The outer layer forms a sac around the inner layer. There is a small amount of fluid between the 2 layers so that the organs can move easily.
The mesothelium has different names, depending on where it is in the body. The mesothelium that protects and cushions the lungs is called the pleura. The inner layer that covers the lungs is called the visceral pleura. The outer layer that lines the inside wall of the chest is called the parietal pleura.
The mesothelium that covers the abdominal organs and lines the walls of the abdomen and pelvis is called the peritoneum. The inner layer is called the visceral peritoneum. It covers and supports most of the internal abdominal organs. The outer layer is called the parietal peritoneum. It lines the walls of the abdomen and pelvis.
The mesothelium is made up of mesothelioma cells. These cells sometimes change and no longer grow or behave normally. These changes may lead to non-cancerous (benign) tumors, such as fibrous tumor of the pleura and multi-cystic mesothelioma. But in some cases, changes to the mesothelioma cells can cause malignant mesothelioma.
Mesothelioma is a very rare type of cancer. It usually starts in the pleura, which is called pleura mesothelioma. This type of cancer makes up 70% to 80% of all mesothelioma’s. Cancer can also start in the peritoneum, which is called peritoneal mesothelioma. This type of cancer makes up about 25% of all mesothelioma’s.
Rarer types of mesothelioma can also develop. This includes pericardial mesothelioma, which starts in the membrane that surrounds the heart. Another rare type is mesothelioma of the tunica vaginal’s testis, which starts in the outer lining of the testicle.
Pleura mesothelioma starts in the membrane that covers the lungs, called the pleura. It is the most common type of mesothelioma. More men than women are diagnosed with pleura mesothelioma.
Peritoneal mesothelioma starts in the peritoneum, which lines the inside of the abdomen and covers many of the organs in the abdomen. This is the 2nd most common type of mesothelioma. Men and women are equally affected by peritoneal mesothelioma.
The following cancerous tumors of the mesothelium are very rare.
- Pericardial mesothelioma
- Mesothelioma of the tunica vaginalis
Pericardial mesothelioma starts in the sac surrounding the heart (the pericardium). The most common symptoms of pericardial mesothelioma are heart problems caused by the tumour or buildup of fluid around the heart. These include chest pain, chest pain that gets worse with deep breathing or coughing, problems breathing, and feeling anxious or restless. Another symptom is palpitations, where the heart feels like it is fluttering, pounding or racing. Treatment may include surgery, radiation therapy or chemotherapy. Pericardial mesothelioma has a very poor prognosis (predicted outcome).
Mesothelioma of the tunica vaginalis starts in the layer that covers the testicles (the tunica vaginalis). The most common symptoms are pain and swelling of the testicle. Treatment is surgery to remove the testicles and the scrotum and the lymph nodes in the area. Radiation therapy may be offered after surgery. The role of chemotherapy in treatment of mesothelioma of the tunica vaginalis isn’t known because the disease is very rare.
Mesothelioma cell types
There are 3 main cell types of mesothelioma.
- Epithelioid is the most common mesothelioma cell type. This type has a more favorable prognosis than the other cell types.
- Sarcomatoid, also called fibrous, is the 2nd most common mesothelioma cell type. This type of cell spreads more quickly than epithelial cells.
- Mixed, or biphasic, have both epithelial and sarcomatoid areas within the tumour. Tumors with more epithelial cells have a better prognosis than tumors with more sarcomatoid cells.
A non-cancerous, or benign mesothelioma is a growth of the mesothelium that does not spread (metastasize) to other parts of the body. Benign mesothelioma tumors are not usually life-threatening. They are typically removed with surgery and do not usually come back (recur). There are a few types of benign mesothelioma.
Fibrous tumour of the pleura
This tumour can start in the thin tissue covering the lung (visceral pleura). It may also start in the thin tissue that lines the chest cavity and surrounds the lungs (parietal pleura). Fibrous tumors of the pleura can cause many of the same symptoms as malignant mesothelioma, such as shortness of breath.
These types of tumors may recur after surgery. In some cases, a localized fibrous tumour of the pleura is actually cancerous.
Multi-cystic mesothelioma forms many benign cysts on the thin lining of the inner abdomen, called the peritoneum. This type of mesothelioma is more commonly found in women. It may also be called benign cystic mesothelioma.
This type of benign mesothelioma can start in the mesothelium lining the reproductive organs. In women, it can start in the Fallopian tubes. In men, it can start in the epidermis ducts that carry the sperm cells out of the testicles.
Risk factors for mesothelioma
A risk factor is something that increases the risk of developing cancer. It could be a behavior, substance or condition. Most cancers are the result of many risk factors. Exposure to asbestos is the most important risk factor for mesothelioma.
Mesothelioma affects men much more often than women. This is probably because men are more likely to be exposed to asbestos at work.
Mesothelioma develops 15–40 years after someone is exposed to asbestos. As a result, it is uncommon in people under the age of 50 and the incidence of mesothelioma increases with age.
Risk factors are generally listed in order from most to least important. But in most cases, it is impossible to rank them with absolute certainty. Research shows that there is no link between smoking and a higher risk for mesothelioma.
Known risk factors
There is convincing evidence that the following factors increase your risk for mesothelioma.
Asbestos is the name of a group of minerals that occur naturally. It can be separated into long, thin fibers that are very fine. When someone breathes in these fibers, they can make their way to the smallest airways of the lung and into the mesothelium. The fibers get into the pleura, where they can eventually cause pleura mesothelioma. If they are coughed up and then swallowed, asbestos fibers can also settle in the peritoneum. This is the most likely cause of peritoneal mesothelioma.
The link between asbestos and mesothelioma has been well known for many years. According to the International Agency for Research on Cancer (IARC) and the US National Toxicology Program, all forms of asbestos are known to cause cancer. Most people with mesothelioma have a history of asbestos exposure.
Occupational exposure to asbestos is the strongest and most common risk factor for mesothelioma. The risk is related to how much asbestos you were exposed to and how long the exposure lasted. People exposed at an early age, for a long period of time and to greater amounts of asbestos are more likely to develop mesothelioma.
Asbestos has been widely used in building materials and many industries. People who may come into contact with asbestos while working include:
- workers in asbestos mines or mills
- construction workers, carpenters and painters
- shipyard workers
- cement plant workers
- insulation workers
- plumbing and heating tradespeople
- demolition workers
- automotive industry workers, including brake and clutch repair workers
- people who work in buildings where asbestos was present and was disturbed during renovations
People who live near an asbestos mine or mill are also exposed to asbestos or asbestos dust in the air. Family members may also be exposed to asbestos from fibers that are brought home on a worker’s clothing.
Occasionally, mesothelioma develops in people who have never been exposed to asbestos.
Erionite is known to cause cancer in people, and it is linked to pleura and peritoneal mesothelioma. It is a naturally occurring mineral that belongs to a group of minerals called zeolites. Zeolites are chemically related to asbestos and erionite has asbestos-like fibers.
Erionite is common in the soil in parts of Turkey. Materials made with erionite are used in construction in these regions. As a result, there are high rates of mesothelioma in these areas due to exposure to erionite.
Fluoro-edenite fibrous amphibole
Fluoro-edenite fibrous amphibole is a naturally occurring mineral that is similar to asbestos, with asbestos-like fibers. It is found in lava flows on the sides of volcano’s, especially on Mount Etna in Italy. Exposure to this mineral increases the risk of mesothelioma.
People given radiation therapy to the chest or abdomen to treat lymphoma, breast, lung or other types of cancer have a higher risk for mesothelioma.
Thorium dioxide (Thorotrast) is a radioactive contrast medium that was once used for imaging tests. People who were given thorium dioxide have a higher risk of developing mesothelioma many years after being exposed to it. Because it was found to increase the risk of some cancers, thorium dioxide is no longer used.
BAP 1 gene mutation
The BAP 1 gene is also called the BRCA1 associated protein 1 gene. It is a type of gene that helps control cell growth and may limit the growth of cancer cells (called a tumour suppressor gene). A rare mutation in the BAP 1 gene may increase the risk for mesothelioma and melanoma of the skin and eye. Healthcare professionals may refer to people who have the BAP 1 gene mutation as having BAP 1 cancer syndrome.
People who are exposed to asbestos and have the BAP 1 gene mutation are at an even higher risk of developing mesothelioma.
Unknown risk factors
It isn’t known whether or not the following risk factors are linked with mesothelioma. It may be that researchers can’t show a definite link or that studies have had different results. More research is needed to see if these are risk factors for mesothelioma:
- simian virus 40 (SV40)
- carbon nanoparticles
Reducing your risk for mesothelioma
You may lower your risk of developing mesothelioma by doing the following.
Avoid exposure to asbestos
Try to avoid any exposure to asbestos.
If you work with asbestos, take proper safety precautions to limit your exposure. Use all the protective equipment provided by your employers. Follow recommended occupational health and safety procedures.
If you have asbestos in your home, have it removed by a qualified asbestos removal expert. Do not try to remove it yourself to avoid exposing you and your family to the asbestos fibers.