Malignant pleural mesothelioma is the most common type of mesothelioma, making up over two-thirds of all cases. pleural mesothelioma affects the lining of the lung and chest cavity known as the pleura.
The pleura is made up of the parietal and visceral pleura. The parietal pleura lines the chest wall and diaphragm while the visceral pleura lines the lungs.
Asbestos fibers work their way into the smallest passageways of the lungs and then into the pleura. Once there, an unknown chemical reaction causes cancerous cell development. As the cells begin to divide abnormally, the pleural lining thickens and excess fluid may accumulate. Pleural thickening gradually contracts the breathing space, causing shortness of breath—often the first symptom for pleural mesothelioma. The fluid, once carefully measured to allow smooth movement between the lungs and other organs, now causes increased pressure, further hindering breathing. This excess fluid is often seen on X-rays, and is referred to as a pleural effusion.