Malignant Mesothelioma

Malignant mesothelioma is a form of asbestos cancer that affects the thin tissue layer that surrounds the body's internal organs, a lining called the mesothelium.

How Many and What Type of Malignant Mesothelioma Deaths Occurred in 1999.

Medical professionals divide malignant mesothelioma into various categories depending on which area of the mesothelium is affected.

The most common form of malignant mesothelioma is pleural mesothelioma, which affects the pleural lining of the lungs. Peritoneal mesothelioma is the second most common form and affects the lining of the abdomen. This type accounts for approximately 10 to 20 percent of malignant mesothelioma cases. In much rarer cases, malignant mesothelioma can occur in the pericardium, the lining of the heart, or the tunica vaginalis, the lining around the testicles.

The only known cause of malignant mesothelioma is asbestos exposure. This form of cancer develops when asbestos fibers are inhaled or ingested and lodge in the pleura, peritoneum, or pericardium. Over time the fibers cause scarring and inflammation, and can eventually lead to cancer. The typical latency period between initial exposure and diagnosis of mesothelioma is between 20 and 50 years. Not everyone who is exposed to asbestos will develop malignant mesothelioma, yet there is no known minimum level of exposure that is considered free of the potential to cause disease later in life. Some persons who have been exposed to asbestos may develop less severe asbestos-related conditions, such as pleural plaques.

Types of Malignant Mesothelioma

In histological terms, malignant mesothelioma is divided into four types: epithelial, sarcomatoid, biphasic, and desoplastic (a variant of sarcomatoid mesothelioma). These classifications pertain to the shape and structure of the cancer cells.

Diagram of Malignant Mesothelioma Types.

Between 50 to 70 percent of malignant mesothelioma cases are epithelial, approximately 7 to 20 percent are sarcomatoid, and 20 to 35 percent are biphasic.

Diagnosing what type of malignant mesothelioma a patient has can be challenging. One contributing factor is that it can be difficult to differentiate mesothelioma from adenocarcinoma on small tissue specimens.

Treatment options are the same for every type, though some are handled more aggressively than others.