Mesothelioma Cell Types can be broadly classified as Epithelioid, Sarcomatoid and Biphasic, with rare subtypes. These are differentiated based on based on their appearance under a microscope and how they grow to form cancerous tumors in the body.
Mesothelioma is a rare form of cancer, diagnosed in approximately 2,000 to 3,000 people each year in the United States. Mesothelioma are tumors that affect the mesothelium, the protective, cement-like lining and sac around most major organs in the body. A primary risk factor for developing mesothelioma is long-term or heavy exposure to asbestos, although it may also be linked to genetic factors, exposure to radiation, or infection from the SV40 virus.
The mesothelium creates a slippery, protective surface around organs that enables them to slide easily against each other when they move, such as when the heart beats or the lungs expand and contract. If the mesothelium is damaged, such as by asbestos fibers, the cells may begin to develop abnormally and out of control, leading to mesothelioma.
The mesothelium has different names, according to the parts of the body it is found in. Accordingly, mesothelioma has different names depending on where it occurs in the body:
- Pleural Mesothelioma – This affects the pleura, or mesothelium of the lungs and chest cavity.
- Peritoneal Mesothelioma – This affects the peritoneum, or mesothelium of the abdominal region.
- Pericardial Mesothelioma – This affects the pericardium, or the mesothelium around the heart.
- Mesothelioma of the Tunica Vaginalis Testis – This affects the mesothelium of the testicular region.
In addition, malignant mesothelioma is also typically divided into three sub-types, depending on the cells found: the epithelioid, the sarcomatoid, and biphasic(a combination of epithelioid and sarcomatoid) mesothelioma. The cell types are identified by the way that they appear under the microscope. When mesothelioma occurs in patients, they may show more than one cell type.
Different Mesothelioma Cell Types
Epithelioid mesothelioma is the most common form of Mesothelioma Cell Types, occurring in between 50 and 70 percent of malignant mesothelioma cases. Epithelioid cells are so named because they have an appearance similar to epithelial cells, which are cells that line the organs and cavities throughout the body. The prognosis for survival with this type of mesothelioma is the most promising of all types.
Sarcomatoid mesothelioma is the least common type of Mesothelioma Cell Types. It occurs in approximately 10 to 15 percent of mesothelioma cases. These cells appear, under the microscope, as elongated spindle-shaped cells. They have an irregular shape and may frequently overlap one another. Diagnosis of sarcomatoid mesothelioma can be difficult because the cells resemble another type of cancer, pulmonary sarcomatoid carcinoma.
Biphasic mesothelioma is the second most common form of Mesothelioma Cell Types. It is found in approximately 20 to 40 percent of all mesothelioma cases. Biphasic mesothelioma tumors have both epithelioid and sarcomatoid cells. These cells do not appear to be mixed together, but rather are found in groupings within a tumor. This grouping typically requires tissue samples to be taken from a few parts of a tumor to make a correct diagnosis. Unfortunately, this type of mesothelioma is generally the most difficult type of mesothelioma to treat; biphasic cells are often more treatment-resistant. This means that biphasic mesothelioma usually requires more aggressive treatment.
The prognosis is generally the best for people with epithelioid mesothelioma, which is an average of eight and a half months. For sarcomatoid, the average survival rate is seven months and for biphasic mesothelioma, it is six months.