Malignant mesothelioma is a type of cancer that arises from mesothelial surfaces that protect internal organs. The most common site of mesothelioma is in the pleural cavity, surrounding the lungs, which accounts for approximately 75% of reported cases. The second most common site, accounting for 25% of cases, is the peritoneal cavity, surrounding the abdomen and pelvis. Other sites that have been reported include cases that involve the pericardium, or lining surrounding the heart, and the tunica vaginalis, which surrounds the testes.
Malignant mesothelioma presents most commonly in people between the ages of 50 and 70. However, it can occur as early as the twenties and throughout life. There are approximately 2200 new cases of mesothelioma every year in the United States. Incidence in Canada is roughly 25% of that in the US, with over 500 new cases of mesothelioma annually in Canada. Diagnosis of mesothelioma is often difficult and as a result, it is considered to be under-diagnosed. Pleural mesothelioma often presents symptoms similar to lung cancer, and can be clinically misdiagnosed as such. Peritoneal mesothelioma is also often mistaken for other tumours that arise in the abdomen, such as bowel cancer and liver cancer.
Mesothelioma is primarily caused by exposure to asbestos. The lifetime risk of developing mesothelioma amongst workers exposed to asbestos is thought to be as high as 10%. A relationship has been shown to exist between the amount of asbestos exposure a person has received and the probability of developing malignant mesothelioma. That is to say, the more someone has been exposed to asbestos, the greater their chances of developing mesothelioma. There is on average a 30 to 40 year latency period between asbestos exposure and the development of mesothelioma. Since Canada was a large producer and exporter of asbestos, the problem of mesothelioma is expected to persist in our country for some time into the future.
Treatment for mesothelioma is highly specialized and requires expertise in surgical, chemotherapeutic and radiation techniques. See treatment options for more information.