Malignant mesothelioma is a rare cancer that develops in the thin layer of tissue, called the mesothelium, that surrounds most of the body’s internal organs. There are different types of mesothelioma, depending on which portion of the mesothelium is affected. The various types of mesothelioma include:
Pleural mesothelioma, which occurs in the tissue protecting the lungs and is the most prevalent form of the disease.
Peritoneal mesothelioma, which is found in the tissue surrounding the abdominal organs.
Pericardial mesothelioma, which is located in the tissue around the heart.
Mesothelioma of the tunica vaginalis, which is seen in the lining around the testicles.
According to the American Cancer Society, from 2,000 to 3,000 people are diagnosed with mesothelioma in the United States every year. Most of the deaths from mesothelioma are caused by exposure to asbestos that occurred decades ago. Because of the sharp decline in the use of asbestos over the last few years, researchers estimate that the number of mesothelioma deaths in this country will probably peak by the year 2010.
It is thought that new cases of mesothelioma will continue to be the result of the extensive use of asbestos in the past. Of course, new cases may develop due to exposures to asbestos that occur during the demolition or repair of older, asbestos-contaminated buildings if proper care is not taken to protect workers and those living and working nearby.
Since 1971, the Occupational Safety and Health Administration (OSHA) and the Environmental Protection Agency (EPA) have attempted, with regulation, to reduce the amount of asbestos to which workers and the public are exposed. Still, as late as 2003, 20% of air samples studied by OSHA in the construction industry exceeded OSHA’s regulatory limits. In addition, though asbestos has been removed from many products that once contained the dangerous substance, asbestos is still being imported and used in the United States in a number of construction and transportation products. To be certain that deaths from mesothelioma do indeed decline, very careful control must be taken to prevent exposure to the asbestos that continues to be used in America.
Benign Pleural Mesothelioma
Benign pleural mesothelioma is a type of noncancerous (benign) tumor that sometimes occurs in the chest. Benign mesothelioma, however, does not generate from the same cells in which malignant mesothelioma begins. And in a small percentage of cases, benign mesothelioma is quite aggressive. Thus, the tumor is also known by a more descriptive name, “solitary fibrous tumor.”
Because solitary fibrous tumor usually does not cause symptoms, it generally is discovered during unrelated tests and procedures. Solitary fibrous tumor most often is treated with surgery. Unlike malignant mesothelioma, solitary fibrous tumor is not linked to asbestos exposure.
Asbestosis is a progressive disease that may develop fully in seven to nine years and may cause death as early as 13 years after the first exposure. In many cases, though, the latency period is 20 years or more. When asbestos fibers (sometimes so small they are invisible) are inhaled, they lodge in and irritate the lung. This irritation sets up a reaction — an inflammation in the small air tubes and sacs of the lung. As the inflammation heals, it leaves scar tissue, called fibrosis. In the lung, this fibrosis causes the lining of the air sacs to thicken so that it is hard for oxygen to pass from the air into your bloodstream. Slowly, as the scarring progresses, the worker begins to suffocate.
This lack of oxygen and hard breathing puts a strain on the heart, so a worker suffering from asbestos may either die of suffocation or of a weak heart leading to heart failure. This entire process is called asbestosis. (Asbestosis is not the same thing as cancer, although both asbestosis and cancer are caused by asbestos exposure.)
Once the process of fibrosis or scarring starts in asbestosis, it is irreversible and progressive. A worker suffering from asbestosis will begin to notice shortness of breath, a dry cough, and sometimes pain in the upper chest or back. As the ability to breathe is limited, fingers and toes become “clubbed” — rounded with flattened nails. This is a sign of decreased oxygen reaching the blood. Because these are vague symptoms, it is easy for doctors to blame them on other causes instead of asbestos exposure. These may be the only symptoms as the disease progresses, so early diagnosis is important.
Cancer is the most serious hazard of exposure to asbestos and it takes less exposure to asbestos to cause cancer than it does to cause asbestosis. Early diagnosis is difficult, the cancer spreads rapidly, and it can rarely be cured. Two kinds of cancer are very strongly related to asbestos: lung cancer and mesothelioma. Lung cancer caused by exposure to asbestos is the same type of cancer that is caused by smoking. When a person exposed to asbestos is also a smoker his chances of getting lung cancer are much greater.
In addition, asbestos also causes cancer of the throat, stomach, esophagus, and bowel. Gastrointestinal cancers such as esophageal, laryngeal, stomach, colon and rectum have been connected to asbestos exposure. These cancers are thought to be caused by swallowing asbestos fibers.