Doctor's Notes on Mesothelioma
Mesothelioma is an uncommon type of cancer that affects the mesothelial cells, which are a layer of specialized cells that line the body cavities and internal organs. Mesothelioma of the lining of the lungs (pleural mesothelioma) is the most common form of all mesotheliomas. The most common cause of mesothelioma is asbestos exposure. Asbestos likely physically irritates the cells, which is believed to cause cancer.
Symptoms of pleural mesothelioma may not occur until 30 to 50 years after exposure to asbestos. The onset of symptoms is gradual, and a person can experience symptoms for four to six months before a diagnosis is made. Symptoms of pleural mesothelioma include difficulty breathing (the most common complaint), chest discomfort, chest pain, cough, easy fatigability, fever, and weight loss.
Symptoms of mesothelioma may not appear until 30 to 50 years after exposure to asbestos. The onset of symptoms is gradual, and a person often experiences symptoms for four to six months before the diagnosis is made.
You should see a health-care provider if you have any of the following symptoms:
- Difficulty in breathing (dyspnea) is the most common complaint
- Chest discomfort
- Chest pain
- Easy fatigability
- Weight loss
The above listed symptoms may be caused by mesothelioma or by other, less serious diseases. Only a health-care provider can make a diagnosis with the help of various exams and tests.
The major known cause of mesothelioma is exposure to asbestos. A known history of asbestos exposure is present in a majority of 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.
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. In humans, the possibility of SV40 serving as a cofactor in the development of mesothelioma is inconclusive and further research is ongoing.
In the most basic terms, cancer refers to cells that grow out-of-control and invade other tissues. Cells may become cancerous due to the accumulation of defects, or mutations, in their DNA. Certain inherited genetic defects (for example, BRCA1 and BRCA2 mutations) and infections can increase the risk of cancer. Environmental factors (for example, air pollution) and poor lifestyle choices—such as smoking and heavy alcohol use—can also damage DNA and lead to cancer.
Most of the time, cells are able to detect and repair DNA damage. If a cell is severely damaged and cannot repair itself, it usually undergoes so-called programmed cell death or apoptosis. Cancer occurs when damaged cells grow, divide, and spread abnormally instead of self-destructing as they should.
Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.