Your organs, including the heart and lungs, are wrapped in a type of tissue called the mesothelium. It keeps them from rubbing against each other. There are several different types. The mesothelium lining that covers your lungs is called the pleura. The pericardium covers your heart. The peritoneum covers your abdominal organs. In men, the tunica vaginalis covers testicles. 

Mesothelioma is the name for cancer that begins in any of these mesothelium cells. Though any of these four areas can be affected, about three-quarters of cases of mesothelioma originate in the pleura.

Mesothelioma is linked to asbestos exposure. Asbestos—a naturally occurring, heat-resistant fiber—was commonly used in insulation, roofing and other building materials through the 1970s. But its usage has drastically declined in the last several decades because it is now known to be dangerous to your health. 

Though the number of cases of mesothelioma have gone steadily down over the past 40 years, roughly 3,000 cases are still diagnosed in the U.S. every year. Mesothelioma affects more men than women. And it can occur 30 or even 40 years after exposure to asbestos.

Mesothelioma is a difficult cancer to treat because it tends to spread to nerves and blood vessels. Current treatments can help relieve symptoms and possibly prolong life. Mesothelioma may be treated with surgery, radiation therapy and chemotherapy. Sometimes targeted therapy and immunotherapy are used as well.

“Mesothelioma is a rare cancer,” says Yale Medicine’s Anne Chiang, MD, PhD, a medical oncologist who treats lung cancers, “but there is still active clinical research, for example, with immunotherapy that is ongoing to try to improve the lives of patients with this disease.” 

Mesothelioma is an aggressive cancer of the mesothelial cells, which form a protective layer of tissue surrounding most of your organs. An estimated 85 percent of mesothelioma cases begin in the pleura in men, and about 75 percent of cases originate in the pleura in women.

The four types of mesothelioma are named for the area of the body where the cancer originates:

• Pleura mesothelioma (lungs)
• Peritoneal mesothelioma (abdominal organs)
• Pericardial mesothelioma (heart)
• Mesotheliomas of the tunica vaginalis (testicles)

Mesothelioma can also be classified into three different categories, based on the types of cells from which the cancer comes. These include epithelioid (50 percent of mesotheliomas), sarcomatoid (10 percent of mesotheliomas), and biphasic, or mixed (40 percent of mesotheliomas).

Unlike most other cancers of the lung, mesothelioma is not caused by smoking tobacco. Here in the U.S., the only known risk factor for mesothelioma is exposure to asbestos. Millions of people were exposed to asbestos as builders, factory workers and construction workers. Others were exposed through the clothing of a family member exposed to asbestos.

Symptoms of mesothelioma include coughing, trouble breathing, and pain under the rib cage. Pain or swelling in the abdomen, lumps in the abdomen, constipation, blood clots, weight loss for no reason and fatigue can also occur.

The symptoms of mesothelioma resemble those for lung cancer, so a doctor will usually begin diagnosis by asking about history of exposure to asbestos. A chest X-ray and/or CT scan to check for issues around the chest and lungs will be ordered.

 If cancer is suspected, a biopsy to remove a small bit of tissue from the pleura, or a small sample of fluid from the pleural space will be needed to confirm mesothelioma. If mesothelioma is suspected in other areas of the chest or abdomen, other types of biopsies may be recommended.

Mesothelioma is an aggressive cancer. Treatment decisions will depend on your overall health and whether the cancer has spread to other areas of the body. Recommended treatments include the following:

• Surgery is used to remove the tumor and some healthy tissue surrounding it. Surgery can also include removing a lung and part of the mesothelium affected.
• Radiation therapy uses high-energy waves to kill cancer cells and stop them from growing. Radiation therapy can also be used to alleviate symptoms caused by mesothelioma.
• Chemotherapy uses anti-cancer drugs to kill cancer cells and stop new ones from growing; it is often recommended for advanced mesotheliomas. 

“Mesothelioma needs to be managed by a great, multi-disciplinary team, including medical oncologists, radiation oncologists and surgeons, who work together to treat this disease and its complications and who participate in clinical trials to advance the care of these patients,” says Dr. Chiang.