Mesothelioma is divided into three main types. These types are based on how the cancer cells look under the microscope.
Epitheloid – is the most frequent type accounting for approximately 50 -70 percent of malignant mesotheliomas. Adenocarcinoma (a type of cells that account for most breast cancers) and mesothelioma cancer cells are of similar shape under the microscope, thus the initial diagnosis can be mistaken unless a biopsy is performed (removal of a section of the suspect tissue) and it is only under closer examination of an ultra powerful microscope that the cells can be uniquely identified.
Sarcomatoid – is the least common of the three cellular types and accounts for approximately 7-20 percent of mesotheliomas. Sarcomatoid mesothelioma is very aggressive and cells tend to be more active producing other malignant cells at a greater rate thus spreading to secondary tissues such as, muscles, bone, cartilage, and fat.
Biphasic – is a combination of the above two types and accounts for approximately 20-35 percent of mesotheliomas. Unlike epitheloid and sarcomatoid cells, biphasic cells do not possess a unique cell structure and are typically arranged in groups within a tumour. Multiple biopsies are generally carried out by a Histopathologist to ensure that both epitheloid and sarcomatoid cancer cells are not overlooked.