The type of Mesothelioma is determined by the location in which the tumor begins and the type of cells that the tumor attacks. The most common form, as many as eighty percent of all diagnoses, is pleural, where the cancer attacks the pleural tissue surrounding the lung. The next most common type is peritoneal, which develops in the majority of other cases and attacks the abdomen. While pericardial and tunica vaginalis are also possible forms of the disease, they are very rare.
Mesothelioma gets its name because of the mesothelium, which is the membrane that surrounds many of the body’s vital organs, and it is where the cancer develops when asbestos is inhaled or ingested.
The form is determined by the location in which the tumor begins, known as its origin site, and the type of cells that the tumor invades, known as its histological subtype. Each type may require a different treatment.
The histological subtype refers to the type of cells that the tumors invade. There are three histological subtypes:
- epithelioid, which attacks epithelial cells,
- sarcomatoid, which attacks sarcomatous cells, and
- bi-phasic, where the tumor attacks both epithelial and sarcomatous cells.
The identification of the proper subtype is an important diagnostic factor because it greatly affects the disease’s prognosis. Epitheloid has the best response rate for treatment, while sarcomatoid has the worst.
Mesothelioma and Asbestos
There are approximately 3,000 diagnoses cases of this deadly disease in the United States alone, each year. The only established cause of this cancer is exposure to asbestos, which was used mainly in construction and manufacturing applications through most of the 20th century. Most victims were unwittingly exposed to asbestos at work or while serving in the military. Other victims developed asbestos related cancers due to environmental exposure from loved ones coming home from work with their clothes covered in asbestos fibers. In the United States, asbestos use peaked at 803,000 metric tons in 1973 and then declined to approximately 1,700 metric tons in 2007
Exposure to asbestos is the only confirmed cause of mesotheliom. Unlike many other predominantly pulmonary-related cancers, cigarette smoking has no known causative effect on its incidence, although asbestos workers who smoke do have a much greater likelihood to develop lung cancer, even more so than regular smokers who don’t work with asbestos.
One of the most difficult aspects of the disease to come to terms with is its long latency period, which is the period of time between first exposure to asbestos and the onset of the disease. Asbestos related cancers can develop anywhere between 10 to 70 years after the initial exposure.