What are the risk factors for mesothelioma?

Working with asbestos is the major risk factor for mesothelioma. A history of asbestos exposure at work is reported in about 70 percent to 80 percent of all cases. However, mesothelioma has been reported in some individuals without any known exposure to asbestos.

Asbestos is the name of a group of minerals that occur naturally as masses of strong, flexible fibers that can be separated into thin threads and woven. Asbestos has been widely used in many industrial products, including cement, brake linings, roof shingles, flooring products, textiles, and insulation. If tiny asbestos particles float in the air, especially during the manufacturing process, they may be inhaled or swallowed, and can cause serious health problems. In addition to mesothelioma, exposure to asbestos increases the risk of lung cancer, asbestosis (a noncancerous, chronic lung ailment), and other cancers, such as those of the larynx and kidney.

Smoking does not appear to increase the risk of mesothelioma. However, the combination of smoking and asbestos exposure significantly increases a person’s risk of developing cancer of the air passageways in the lung.

What is Mesothelioma?

Mesothelioma (mez-uh-thee-lee-O-muh) is a type of cancer that begins in the tissue that line different organs and spaces inside the body. This tissue, called mesothelium (mez-uh-thee-le-um), protects organs by making a special fluid that allows the organs to move. For example, this fluid makes it easier for the lungs to move during breathing.

Mesothelium surrounds the lungs, the stomach, the heart, and other organs. Tumors can start in any of these places. These tumors can be benign or they can be cancerous. The information that follows covers only those that are cancerous.

There are three main types of mesotheliomas. The most common (50%-70%) is the epithelioid type. This type has the best outlook. The other two types are less common. The treatment choices for all three are the same.

About three out of four mesotheliomas start in the chest cavity. These are called pleural mesotheliomas. Another 10%-20% begin in the abdomen (peritoneal mesotheliomas). Those starting around the heart are very rare. This cancer can also start in the tissue around the testicles, but this is also very rare.

There are also benign (not cancer) tumors that can start in the mesothelium, but the information here applies only to malignant (cancerous) mesotheliomas.