Causes of Different Types of Mesothelioma

A common source

The only known cause of malignant mesothelioma in the United States is asbestos exposure.  About two-thirds of all cases are pleural mesothelioma, affecting the mesothelial membranes that lie along the surface of the lungs.  The majority of other cases, such as peritoneal mesothelioma, involve the peritoneal membranes of the abdomen.  The rarest are cases found in the pericardium around the heart or in the genital system.  Each type produces different mesothelioma symptoms.

All types of mesothelioma result from exposure to asbestos dust and fibers years before the disease develops.  The mechanisms by which the asbestos triggers the different mesothelioma symptoms are continually being studied.  Researchers have many questions about the causes of mesothelioma and whether the disease becomes established differently depending on where it develops in the body.

How asbestos damages cells

Researchers have a theory about how asbestos damages the body that follows this sequence:

• Asbestos particles remain dormant in the body for many years, producing no symptoms.
• Asbestos irritates and inflames mesothelial cells, resulting in scarring and other types of cell damage.
• The asbestos fibers disrupt cell functions that are necessary for normal cell division, resulting in the runaway cell division of cancer.
• Asbestos stimulates production of free radicals, molecules that disrupt DNA and cause cells to mutate into cancer.

Although researchers know that asbestos causes similar damage to different cells, how the asbestos gets into the position to harm different parts of the body (for example, peritoneal vs. pleura cells) remains at least partially unexplained.

Inhaling asbestos fibers

When materials containing asbestos are manipulated, fibrous particles are released into the air as fine dust.  People nearby inhale these jagged particles into their lungs, where they become stuck because of their unique characteristics.  Eventually, these asbestos fibers travel through the lungs, cause damage to the pleura, and cause pleural mesothelioma.  Researchers believe that migration of the inhaled particles from the lungs to the heart is what leads to the eventual development of pericardial mesothelioma.

Mesothelioma by digestion?

Less clear are theories about acquisition of peritoneal mesothelioma by digestion.  Some researchers believe that inhaling asbestos fibers allows them to be caught in mucous in the throat or that fibers are eaten when asbestos dust settles on food.  They then are swallowed and introduced directly to the gastrointestinal tract.

Others believe that the fibers inhaled into the lungs travel to the peritoneal area via the blood stream or lymphatic system.  In the case of the rare form of mesothelioma that affects the testicles, researchers think that the asbestos fibers migrate from the stomach area to become lodged in the portion of the peritoneum surrounding the scrotum.