Peritoneal mesothelioma is a rare form of the asbestos cancer: mesothelioma; which is caused by asbestos exposure. It develops in the abdomen, in the mesothelial cells that line the peritoneum. Approximately 1/10 to 1/20 of the 2,000 to 3,000 Americans diagnosed with cases of mesothelioma annually are diagnosed with peritoneal mesothelioma.

The peritoneum is a membranous layer that is made up of two 'sub-layers' called the parietal and visceral layers. The parietal layer covers the abdominal cavity, while the visceral layer surrounds abdominal organs. Together these two layers provide support and protection for abdominal organs and the abdominal cavity as a whole.

Peritoneal mesothelioma, like all types of mesothelioma, is caused by asbestos exposure. There are two main theories regarding how asbestos exposure leads to the development of peritoneal mesothelioma:

1) Asbestos fibers are ingested. Afterwards they work through the digestive system and into the peritoneum.

2) Asbestos fibers are inhaled and they work their way into the lungs through the airways.

Regardless of how the asbestos exposure occurs, they are toxic to the body. The very mechanism of asbestos fibers makes it difficult for the body to rid itself of them naturally.

The fibers become trapped in the peritoneal membrane, and over a period of two or more decades, cause certain changes in the mesothelial cells of the peritoneum. These changes include inflammation which causes cancer. When cells become cancerous, they lose the ability to regulate their own division and growth. Cancerous mesothelial cells divide and grow without restraint, and this uncontrolled cell growth causes thickening of the peritoneum, and the build-up of fluid in the peritoneal layers. Overtime, as cancerous cells continue to divide, tumors form.

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