Mesothelioma cells can be categorized as epithelial or sarcomatoid. Epithelial cells appear to be organized and structured. Malignant epithelioid mesothelioma is the most common form of mesothelioma. While this form of mesothelioma is fatal, like all types of malignant mesothelioma, epithelial mesothelioma can respond favorably to certain treatments. The overwhelming majority of mesothelioma cases are of the epithelial variety.
On the other hand, sarcomatoid cells do not appear to follow any order or structure and generally do not respond to treatment. Mesothelioma in general is a difficult disease to diagnose due to the vague nature of its symptoms. Sarcomatoid mesothelioma is even harder to diagnose, because the cells very often look like healthy cells. There is significant evidence to show that individuals with sarcomatoid mesothelioma have been exposed to higher levels of asbestos. Malignant sarcomatoid mesothelioma is diagnosed in roughly 10 percent of cases.