Pleural Mesothelioma: Mesothelioma of the Pleura
Continued from: Types of Mesothelioma
Pleural mesothelioma is a disease that affects the lining of the lungs, or lung pleura. Sometimes doctors refer to this disease as mesothelioma of the pleura. It is a common misconception that mesothelioma is a type of primary lung cancer; it is not. Mesothelioma is a cancer of the serous membranes. These membranes enclose a number of organs throughout the midsection of the body, including the lungs. The most common type of mesothelioma, pleural mesothelioma, affects the serous membranes of the lungs.
Mesothelioma can also affect the serous membranes surrounding the abdomen, called peritoneal mesothelioma, and the membranes surrounding the heart, or pericardial mesothelioma. When mesothelioma spreads to the lungs from the serous linings of the lungs, abdomen or heart, it is considered secondary lung cancer. Also, pleural mesothelioma is sometimes referred to as an asbestos lung cancer. Technically, cancers that do not originate in the lungs are not considered lung cancer; thus, terms such as secondary lung cancer and asbestos lung cancer (pleural mesothelioma) are misleading. Asbestosis is a type of asbestos lung disease that does originate in the lungs and is often confused with mesothelioma.
Pleural Mesothelioma Cancer
Pleural mesothelioma cancer represents about 75 percent of all mesothelioma cases. This disease is caused by the inhalation of asbestos fibers, which then settle in the lungs. These asbestos fibers become imbedded in the lining of the lung (the pleura). Over time, they cause chronic inflammation that eventually leads to growth of cancerous tumors or, in some cases, asbestosis.
Pleural mesothelioma cancer normally appears as multiple tumor masses affecting the parietal surface (outside; further from the lung) and visceral surface (inside; closer to the lung) of the pleura. Typically, the parietal surface has greater involvement than the visceral. There is a slightly higher incidence of mesothelioma in the right lung, apparently due to the fact that the right lung is larger and has a greater amount of pleural surface area. Also, the lower lungs typically show more tumor masses than the upper lung. This is thought to be due to gravitational factors influencing how the asbestos fibers settle in the lungs after they have been inhaled.
Large growths in the pleura are normally noted in patients upon diagnosis. As the diseases progresses, these growths lead to a complete obliteration of the lung cavity. The tumors can spread from the lung pleura to other organs, including the heart and abdomen. Mesothelioma can also invade the lymph nodes and circulatory system.
Tumors unrelated to pleural mesothelioma also grow in the pleura. These tumors start in other parts of the body and metastasize to the pleura. The most common form of non-pleural mesothelioma cancer that occurs is lung cancer, representing about 36 percent of the cancer occurring in the pleura. The next most common forms are breast cancer (25 percent), ovarian cancer (5 percent) and gastric cancer (2 percent). Lymphoma also accounts for a small portion of cancers that metastasize to the pleura.
Pleural Mesothelioma Symptoms
The most common symptom for pleural mesothelioma patients is chest pain. But, the pain often is not associated directly with the lung pleura and often appears in the shoulder or upper abdomen. Shortness of breath, called dyspnea, is also a symptom. Cough, weight loss and anorexia are present in some patients, but are less common. Finally, the rapid growth of the pleural mesothelioma cancer tumors enlarges the pleural space, causing it to fill with fluid. Oftentimes, this buildup of fluid known as a pleural effusion causes the discomfort or pain associated with first detection of the disease.
Pleural Mesothelioma Prognosis
Most patients' malignant mesothelioma prognosis is quite bleak. In a study involving 167 patients with proven pleural mesothelioma, the median survival rate of patients following diagnosis was 242 days. The survival rate was also affected by the type of mesothelioma cancer cells; patients with biphasic cell types have the shortest life expectancy.
[Page updated January 2010]