Biphasic mesothelioma means that the cells include a mix of both epithelials and sarcomatoids. They are the second most common cellular type of mesothelioma. Because the two types of cells are present, there is no specific structure, and despite the fact that both mesothelioma types are present they tend to form in differentiated groups in different areas of the tumor. Treatment can be difficult because of the resistance of sarcomatoid mesothelioma cells. Treatment is usually based on multi-modal therapy that combines radiation and chemotherapy. Surgery is also an option, but only in early stages.