The pleura is a membrane. It lines the outside of the lungs and the inside of the chest cavity. Pleural mesothelioma is cancer of the pleura.

Pleura of the Lungs
Pleura of the Lungs
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Cancer occurs when cells in the body divide without control or order. If cells keep dividing uncontrollably, a mass of tissue forms. This is called a growth or tumor. The term cancer refers to malignant tumors. They can invade nearby tissue and spread to other parts of the body.

Asbestos is a fibrous mineral that is known to cause cancer. This type of cancer is almost always caused by exposure to it. Even a small amount of exposure can be a risk.Other fibers can cause mesothelioma.