Malignant pleural mesothelioma is an uncommon type of cancer that begins in the mesothelial cells of the pleura. The pleura is a thin membrane that surrounds the lungs and lines the chest cavity. The pleura consists of a visceral surface, which covers the lungs and a parietal surface, which lines the walls of the chest cavity and covers the upper surface of the diaphragm and lungs. The two layers are one continuous sheet of tissue that contains mesothelial cells. There is normally a very small amount of watery fluid within the pleural cavity that lubricates the pleural surfaces and allows the lungs to move freely over the inner surface of the chest wall during breathing.
Malignant pleural mesothelioma is a rare and aggressive cancer that represents about 90 percent of all malignant mesothelioma cases. It’s primarily caused by the inhalation of asbestos, a fiber commonly found in some forms of insulation, vinyl floor tiles, and other material. Tumors form in the pleura, a thin membrane of cells that line the lungs and chest wall.
Malignant pleural mesothelioma is predominantly caused by exposure to asbestos. The association between inhaled asbestos particles and mesothelioma was recognized in 1960.1 Asbestos exposure is also associated with:
- A non-cancerous scarring of the lungs called “asbestosis,” and
- Developing lung cancer, which is worsened by cigarette smoking.
Types of Malignant Pleural Mesothelioma
Doctors classify pleural mesothelioma into 3 distinct categories: epithelioid, sarcomatoid, and mixed-type. Epithelioid is the most common, occurring in 60-70% of patients. However, it may be confused with another type of lung cancer called adenocarcinoma; therefore, special tests are necessary to confirm a diagnosis. The sarcomatoid type (10-20%) is the least common and most aggressive. Mixed-type (20-30%) shows features of both epithelioid and sarcomatoid. Before considering treatment options, patients must have a confirmed diagnosis of mesothelioma and accurate staging of the disease performed.
1 Antman KH, Pass HI, DeLaney T, et al. Benign and malignant mesothelioma. In: Devita VT Jr, Hellman S, Rosenberg SA, eds. Cancer Principles and Practice of Oncology. 4th Edition Philadelphia, PA:JB Lippincott Co;1993:1489-1508.