Histological Subtypes of Cancer
An important tool used in the definitive diagnosis of disease is histology, the microscopic examination of cellular anatomy. Although it is most common for doctors to classify this cancer based on the tumor’s location, there are also various histological sub types of pleural, peritoneal, pericardial and testicular mesothelioma.
Epithelial
Accounting for 50 to 70 percent of all cases, epithelial mesothelioma is by far the most common histological subtype. Compared to other cell types, epithelial mesothelioma typically responds better to treatment. It is therefore the histological subtype associated with the best survival.Sarcomatoid
Cancers that arise from connective tissues are called sarcomas, and sarcomatoid mesothelioma is so named because under the microscope, its cells are elongated and spindle-shaped like those of a sarcoma, overlapping in a disorderly fashion. Between 15% and 20% of all malignant mesothelioma diagnoses are classified as sarcomatoid.
Sarcomatoid mesothelioma is more aggressive than other histologic subtypes of mesothelioma and consequently more difficult to treat. Sarcomatoid mesothelioma cells are notably more resistant to chemotherapy than either epithelial or biphasic mesothelioma. Patients who have been diagnosed with sarcomatoid mesothelioma generally have the lowest survival rates among mesothelioma patients.
Biphasic
A combination of epithelial and sarcomatoid cells within one tumor, biphasic mesothelioma occurs in about 20 to 35 percent of cases. Because the ratio of epithelial to biphasic cells can vary significantly from case to case, the distribution of cells influences survival. A greater number of epithelial cells is generally associated with a better prognosis.
There is no commonly accepted standard for diagnosis among members of the medical community although the World Health Organization recommends that the diagnosis be used when a tumor is comprised of at least 10% epithelial cells and at least 10% sarcomatoid cells.
