Malignant mesothelioma strikes the mesothelium, which is a membrane that covers and protects many organs within the body and lines the chest cavity and abdominal cavity walls. One portion of the mesothelium wraps around the lungs providing an outer lining. Another piece of this membrane lines the chest wall opposite the lung; together these membranes are known as the pleura. This is where seventy percent of all mesothelioma cases occur: in the outer lining of the lungs and the lining of the chest wall – a condition known as pleural mesothelioma. Because it occurs in the lining of the lungs it is sometimes mistakenly referred to as asbestos lung cancer.
Lung Cancer is a tumor that develops within the lungs. It is usually a single growth unlike mesothelioma, which spreads across the pleura surface outside the lung, in the form of many small tumors. Asbestos fibers in the lungs can contribute to the development of lung cancer, usually in concert with a history of smoking. But asbestos is just one of many factors in Mesothelioma lung cancer development; it is the only known cause of mesothelioma.
Mesothelioma – A Cancer with a Single Cause
Various parts of the mesothelium have various names: the peritoneum is the portion of the mesothelium that covers the wall of the abdominal cavity. The pericardium is a sac around the heart. Mesothelioma may develop in either of these locations as well as in the pleura. In each of these cases the cancer is usually diffuse, being an array of small tumors rather than a single large growth.
Because seventy percent of all diagnosed cases of mesothelioma develop in the outer lining of the lungs, it is best known as a cancer that affects the lung area. Some of the symptoms for pleural mesothelioma are similar to those that accompany lung cancer: a chronic, dry cough, chest pain, shortness of breath, and pressure within the chest. Lung cancer can trigger pleural effusion, an accumulation of fluid common to pleural mesothelioma.
However lung cancer as it is traditionally understood is cancer that causes usually a single tumor in the lung. Pleural mesothelioma causes tumors to develop on the surface of the pleura, small tumors over a diffuse area across a thin layer of tissue outside the lung. Pleural mesothelioma and lung cancer are two different forms of carcinoma.
Peritoneal mesothelioma has its own set of unpleasant symptoms generally unrelated to those that accompany lung cancer. Abdominal swelling and pain are common; so are gastrointestinal problems. Pericardial mesothelioma creates symptoms that are very similar to those seen with cardiovascular disease such as irregular heartbeat, heart palpitations and severe shortness of breath.
When Asbestos Causes Lung Cancer
Asbestos is also recognized as a potential primary cause for lung cancer; in fact the way asbestos most often enters the body is through the lungs. Tiny asbestos fibers that have broken off from an asbestos product that is being manipulated or is deteriorating can float in the air like tiny dust particles and be inadvertently inhaled.
These fibers cannot be shed by the body and eventually work their way through the lung to the pleura, the lining outside the lungs. In some instances asbestos fibers stay in the lung and cause asbestosis or worse, the development to malignant cells which become the foundation for asbestos and lung cancer. Asbestos fibers may be a primary cause for lung cancer or a contributing cause, as with cigarette smokers. Far more cases of lung cancer have primary causes that are smoking related.
Like many forms of asbestos cancer mesothelioma may metastasize in its late stages and cause the development of tumors in other areas of the body. Late stage mesothelioma may cause tumors to develop within the lungs; at this point the patient has mesothelioma as the primary form of cancer and lung cancer secondary to pleural mesothelioma.
Three Asbestos Diseases
Asbestos can contribute to everything from bronchitis to emphysema, but there are three diseases for which it can be a primary instigator – all of which can be fatal:
There is no doubt that in past generations mesothelioma was often misdiagnosed as lung cancer by a physician or coroner filling out a death certificate. The frequency of asbestos-caused lung cancer today can be interpreted in many ways.
Ninety percent of all lung cancer cases are primarily attributable to smoking. However second-hand smoke, industrial pollution of all types and radon gas are among significant contributors to the likelihood of lung cancer. The same is true of asbestos. According to one medical source, asbestos exposure increases the risk of lung cancer by nine times. A combination of asbestos exposure and cigarette smoking raises the risk fifty to eighty four times over just smoking.
- Malignant Mesothelioma, American Cancer Society, http://www.cancer.org/Cancer/MalignantMesothelioma/DetailedGuide/malignant-mesothelioma-malignant-mesotheliona
- Mesothelioma Questions and Answers, National Cancer Institute, http://www.cancer.gov/cancertopics/factsheet/Sites-Types/mesothelioma
- Non-Small Cell Lung Cancer, Medline Plus, National Institutes of Health, http://www.nlm.nih.gov/medlineplus/ency/article/007194.htm
- Lung Cancer & Cigarette Smoking, Dr. Fred Grannis MD
- Cigarette Smoking & Asbestos Exposure, Agency for Toxic Substances & Disease Registry, http://www.atsdr.cdc.gov/asbestos/site-kit/docs/CigarettesAsbestos2.pdf