Mesothelioma is classified into three cell types based on how the cancer cells appear under a microscope: epithelioid (50–70% of cases, best prognosis), sarcomatoid (10–20% of cases, most aggressive), and biphasic (20–30% of cases, mixed prognosis). Cell type is determined through biopsy and pathology examination and is one of the most important factors in determining treatment options and expected outcomes.
Epithelioid Mesothelioma
Epithelioid mesothelioma is the most common cell type, accounting for 50–70% of all diagnoses. These cells are uniform in shape, tend to stick together, and spread more slowly than other cell types. Because of these characteristics, epithelioid mesothelioma is the most responsive to treatment — including surgery, chemotherapy, and immunotherapy — and has the best overall prognosis. Patients with epithelioid cell type are more likely to be candidates for surgery and multimodal treatment.
Sarcomatoid Mesothelioma
Sarcomatoid mesothelioma is the rarest cell type (10–20% of cases) and the most aggressive. These cells are elongated, spindle-shaped, and spread rapidly through surrounding tissue. Sarcomatoid mesothelioma is more resistant to treatment and has the poorest prognosis. However, immunotherapy has shown promise for sarcomatoid patients, and clinical trials continue to explore new options. Content about sarcomatoid mesothelioma should be handled with particular sensitivity given the difficult prognosis.
Biphasic Mesothelioma
Biphasic mesothelioma contains both epithelioid and sarcomatoid cells. It accounts for 20–30% of diagnoses. The prognosis depends largely on the ratio of cell types — a tumor with predominantly epithelioid cells has a better prognosis than one with predominantly sarcomatoid cells. Treatment decisions account for the dominant cell type.