Pleural mesothelioma is the most prevalent of all types of mesothelioma. It affects the soft tissue surrounding the lungs known as the pleura or pleural membrane. Mesothelioma tumors can develop in multiple locations throughout the body, but they originate from the pleura in approximately 75 percent of all cases. In each case, cancer forms in the mesothelium, a tissue membrane that protects various organs and body cavities.

Pleural mesothelioma is typically caused by occupational exposure to airborne asbestos fibers. Because this exposure is frequently in male-dominated industries, around 80 percent of all pleural mesothelioma patients are men. Once inhaled into the lungs, needle-like asbestos fibers migrate to the pleural membrane, where the body cannot easily get rid of them. Fibers irritate the pleura, which can result in chronic inflammation and scarring. Infrequently, this causes pleural mesothelioma.

Over an extended period of time – usually three or more decades – asbestos triggers genetic changes in the pleural cells. If the cells become cancerous, they begin to divide uncontrollably, forming tumors that reduce lung capacity and generate excess fluid buildup between the pleural layers.
The overall outlook for pleural mesothelioma patients is poor. This is because symptoms do not usually arise until more advanced stages of cancer where curative surgery is no longer an option. However, an early diagnosis facilitates the most effective treatment options, potentially improving a patient's outlook and life expectancy.