Malignant mesothelioma is a disease that originates in the mesothelial cells that line body cavities. There are four different locations that this disease can be found, the pleura, the abdominal cavity, the sac surrounding the heart, and the lining of the testes. It can be either localized or what doctors refer to as diffuse, which means spread over a wide area. It is difficult to diagnose because an analysis of the fluid buildup that is caused by the disease doesn’t provide a definitive diagnosis. Mesothelioma occurs more frequently in men than women and it typically develops when the patient reaches ages 50 through 70.
About 90 percent of all cases of malignant mesothelioma develop in the pleura.
How Does the Disease Manifest Itself in the Body?
Mesothelioma cell types include epithelial, sarcomatoid and biphasic. Pleural mesothelioma starts as plaques and nodules that are not visible, but they eventually merge together to form a covering in the pleura that resembles a sheet. Tumors begin growing in the lower chest and can penetrate the diaphragm and surround the lung surface.
The disease extends into the functional area of the lung, chest wall, and the tissues that separate the two pleural sacs. It eventually invades the wind pipe, ribs, the vertebrae of the spine, the network of nerves that run from the spine into the arm, and the large vein that brings blood back to the heart from the head, neck and arms.
Mesothelioma cells have extremely complex arrangements of chromosomes within the nuclei that include one incomplete set of chromosomes. Usually it is the loss of a single copy on chromosome 22.
How Frequently Does Mesothelioma Occur?
There are approximately 2500 cases diagnosed annually in this country. The highest incidence of the disease occurs about 35-40 years after the individual has been exposed to asbestos.
The ratio of occurrence between males and females is 3 to 1. There have also been cases of children diagnosed with mesothelioma.
In a study titled “Malignant Mesothelioma in Rome, Italy 1980-1995: a Retrospective Study of 79 Patients”, published in 1996 in Tumori (Tumors), researchers wanted to analyze the characteristics of 79 mesothelioma patients whose data was obtained from the main teaching hospital of Rome, Italy, and other local clinics of Latium Region. Their other objective was to determine the role of asbestos exposure in causing this disease.
The scientists found that 53 percent of the men for whom information was available had occupational exposure to asbestos and more than 50 percent of the women developed the disease because of secondary exposure resulting from contact with someone in the household who worked in a job in which they were exposed to asbestos.
They also observed that occupational exposure resulted from employment as construction workers, railroad workers, naval mechanics and navy personnel, bakers, explosive workers and car mechanics.
These findings led the researchers to conclude that:
“The study confirmed that mesothelioma risk is present in several job titles of the construction industry, and it is no longer confined to workers employed in the manufacture or application of asbestos products. The occurrence of malignant mesothelioma in patients with unexpected occupational and nonoccupational exposures indicates the need for further investigation on previously underestimated exposures.”