Monday, September 4, 2017

What Is Mesothelioma?

An overview of mesothelioma cancer including how asbestos causes mesothelioma, as well as information on types including pleural and pericardial mesothelioma

Mesothelioma is a cancer that derives its name from the fact that the cancer originates from mesothelium, cells that form linings for various organs in the body such as the lungs, heart, abdomen and testicles and the symptoms are related to the anatomical location of the cancer. Mesothelioma kills about 3000 people annually in the United States. The average age of diagnosis is 70 years and older and men are mostly affected which is likely due to the fact that they are most likely to be in occupations that increase their risk for the disease.

What Is Mesothelioma?

The most common form is pleural mesothelioma, cancer of the pleura which lines the lungs. Individuals with this form will often develop a persistent dry or raspy cough, cough up blood, have night sweats, fevers and lose more than 10 percent of their body weight with no obvious explanation. Feeling tired and abdominal and chest pains, shortness of breath with minimal activity and lumps appearing on the chest can be symptoms as well.

Night sweats, fevers, fatigue and unexplained weight loss can also be symptomatic of peritoneal mesothelioma but there may be other symptoms may appear and include a swollen and painful abdomen, anemia, diarrhea or constipation, nausea or vomiting and lumps under the skin.

Pericardial mesothelioma is the form that affects the lining that forms a sac around the heart. Pericardial mesothelioma can manifest as heart palpitation and arrhythmias. Symptoms can mimic those of pleural and peritoneal mesothelioma with symptoms such as trouble breathing during normal activity, fatigue, fever and night sweats. Testicular mesothelioma is very rare.

Mesothelioma typically has a poor prognosis because it is typically diagnosed after it has spread and often develops resistance to treatment. Management and treatment usually focuses on palliative care which focuses on alleviating pain. Surgery, chemotherapy and radiation are often part of the regimen to slow progression and extend survival. Researchers are always looking for new and more effective drugs and procedures that can allow patients to live longer and have a good quality of life.

Mesothelioma is one of the few cancers we can say without a doubt is most commonly caused by asbestos, a compound that is naturally present in the environment and in many construction materials. Most countries have outlawed using asbestos in various products and workers who are exposed to the compound were personal protective equipment. Mesothelioma is the result of several decades of exposure which likely explains an increase in cases in the last few years.

How Asbestos Causes Mesothelioma


Asbestos is not one mineral but a catch all term for six different silicate minerals (amosite, crocidolite, tremolite, anthophyllite, actinolite and chrysotile) that are very flexible, have a high tensile strength, and are highly resistant to destruction by heat, chemicals and electricity. They are present in rocks and soil and were once a component of many construction materials such as insulation, fireproof materials, automotive brakes, textile products, cement and wallboard. Due to the risk of mesothelioma, asbestos has been eliminated from many products.

Asbestos particles are fine and can be short or long. The fact that they are fine makes them particularly dangerous because when inhaled they can get further into the respiratory tract and stay there for a long period of time. Both long and short fibers can get down into the alveoli where oxygen jumps onto red blood cells and dumps carbon dioxide back into the lungs to be exhaled. It is from here that the fibers can get to the pleura. Once in the lungs, the damaged tissue stimulates an immune response and genes that promote cell growth. The immune response causes the immune cells called macrophages to come to the site of injury and engulf them.

The short fibers are generally cleared out, but the long fibers are too big for the macrophages and the immune system continues to react by producing chemicals that cause inflammation. Reactive oxygen species are produced by the macrophages as they continue to try and completely engulf the long fibers which cause more damage to the cells. In general, inflammation is good and has a purpose: come to the site of injury, destroy the foreign substance or pathogen and then leave so the injured tissue can heal. But with chronic inflammation, the cells and chemicals produced never go away and end up damaging the tissue as it is trying to heal. So it becomes this vicious cycle of the tissue healing through DNA replication and cell division and the inflammation causing damage, and as a result, cell division occurs at a higher rate. With this high rate of cell division, the odds that a damaged cell will get through the cell cycle without being repaired or killed by the various proteins that serve as checkpoints increases. Once a damaged cells escapes those mechanisms, that cell can go on to grow and divide uncontrollably which is the beginning of carcinogenesis.

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