Pleural mesothelioma cancer is by far the most frequently occurring form of mesothelioma, accounting for about 75 percent of all mesothelioma cases. Pleural mesothelioma is caused by the inhalation and settling of asbestos fibers in the lungs. Over time these rigid fibers cause scarring of lung tissue and can lead to the development of pleural mesothelioma.

Pleural mesothelioma usually as multiple tumor masses affected both inner and outer portions of the pleura. Tumor masses typically are much more prevalent on the lower portion of the lungs. This is most likely due to the force of gravity causing asbestos fibers to settle in the lower portions of the lungs after being inhaled.

Large tumor growths in the pleura are usually discovered in the mesothelioma diagnosis process. Over time these growths spread to other parts of the lung, eventually affecting the entire lung cavity. Tumors may also spread to other organs parts of the body. This process of progression and spreading to other areas is known as metastasization. Through this process pleural mesothleioma may begin to affect the organs of the abdomen and even the heart. Mesothelioma may eventually make its way into the lymphatic and circulatory systems.

Not all tumors that develop in the pleural are attributable to pleural mesothelioma. In some cases tumors that have developed in other locations of the body may spread or metastasize to the pleura.