Mesothelioma is a rare form of cancer in which malignant (cancerous) cells are found in the sac lining the chest or abdomen. Exposure to airborne asbestos particles increases the risk of developing malignant mesothelioma.

The word Mesothelioma (like other cancer names) is derived from mesothelium, a membrane that covers and protects most internal organs of the body. Mesothelium is composed of two layers of cells, one layer surrounds the organ and the second layer forms a sac around it. Lubricating fluid is produced by the Mesothelium and is released between the layers which help moving organs to flow easily against adjacent structures. Organs such as the heart, lungs and stomach that expand and contract rely on this fluid.

Mesothelium is named differently depending on where it is located in the body. The mesothelial tissue covering the lungs and the chest cavity is the pleura. The tissue covering the organs in the abdominal cavity is the peritoneum. The tunica vaginalis testis covers the male internal reproductive organs and the tunica vaginalis testis surrounds the female reproductive organs. Most cases of Mesothelioma begin in the pleura or the peritoneum. When mesothelioma develops in the pleura (known as pleural mesothelioma), the delicate lining thickens and fluid may collect between the two layers of the pleura. The abdomen peritoneal mesothelioma causes thickening of the lining and a collection of fluid in the abdomen, called ascites. Symptoms are associated with the organs that may be affected by mesothelioma.

Mesothelioma has a long latency period and it's important to determine who needs to be examined. This long silent period makes diagnosis difficult and symptoms may sometimes be mistaken for something else. Treatment options are often determined by the stage of mesothelioma of the patient.

Mesothelioma is serious and life-threatening. By the time cancer is diagnosed the patients survival time is usually short. Mesothelioma usually spreads throughout the peritonal or pleural cavity before diagnosis, and complete surgical removal is unlikely. Because of this, the average survival time is only 1 year. If the cancer is found early, approximately 50% of the patients survive 2 years and approximately 20% survive 5 years. Additionally, unlike with other tumors, chemotherapy and radiation therapy are not very effective.