what is mesothelioma?

It is often hard to diagnose mesothelioma by looking at the cells from the fluid around the lungs, abdomen or heart. It is even hard to diagnose mesothelioma with tissue from biopsies. Under the microscope, mesothelioma can look like several other types of cancer. For example, pleural mesothelioma may resemble some types of lung cancer and peritoneal mesothelioma may resemble some cancers of the ovaries. For this reason, special laboratory tests are often done to help distinguish mesothelioma from some other cancers. These tests often use special techniques to recognize certain markers (types of chemicals) known to be contained in mesotheliomas. Different markers are present in cancer of the lung or ovary. The electron microscope can sometimes be helpful in diagnosing mesothelioma. This microscope can magnify samples more than 100 times greater than the light microscope which is generally used in cancer diagnosis. This stronger microscope makes it possible to see small parts of the cancer cells that distinguish mesothelioma from other types of cancer.
The diagnosis of mesothelioma presents problems primarily initially in the distinction between mesothelioma and other forms of cancer such as adenocarcinoma or benign, noncancerous pleural inflammation. The best diagnostic tools at the moment remain the open pleural biopsy performed during thoracoscopy. This procedure also allows for direct visualization of the inside of the chest, and information of involvment of other organs and extension of disease. Other procedures with lower yields are CT guided pleural biopsy, or blind pleural biopsy. In addition to the gross appearance of the tumor, pathologists often rely on a panel of histochemical and immunohistochemical stains to diagnose or exclude meosothelioma. Currently markers linked to prognosis of mesothelioma are under study, but have not been validated for the general use.