Malignant Sarcomatoid Mesothelioma

Cancer specialists use a variety of different methods to categorize malignant mesothelioma. The most well-known method is categorization of the cancer according to its point of origin in the body. For example, pleural mesothelioma develops in the lining of the lungs, pericardial mesothelioma develops in the lining of the heart, and peritoneal mesothelioma develops in the lining of the abdominal cavity. For more information about the different types of mesothelioma, please see Mesothelioma Overview.

Malignant mesothelioma and other types of cancer are also categorized according to how far advanced each case of cancer is, in terms of factors such as the size of tumor(s), and whether the cancer has spread to lymph nodes or other locations. To read more about how cancers are categorized in this way, please see Mesothelioma Staging Systems - Overview.

In addition, malignant mesothelioma and other asbestos cancers are categorized according to the size, shape, and general appearance of cells when viewed under a microscope, as well as the types of proteins that can be detected on the surface of the cells. This type of categorization is called histology, or histopathology.

Each of these systems of categorization provides mesothelioma specialists with important information that is used to determine the exact type of cancer cells they are dealing with in a given case. This information is then used to determine how to treat each patient on an individual basis.

Biopsy and Histopathology

Patients who undergo medical evaluation to determine if they have malignant mesothelioma will undergo a variety of medical tests that determine the location and nature of the cancer. One of these is a biopsy of cells that are suspected to be cancer cells. During a biopsy samples of suspected cancer cells are removed from several different locations in the tumor site. These cell samples are then evaluated in a laboratory to determine what type of cells they are and whether the cells are malignant. For more information about biopsy procedures a mesothelioma patient might undergo, please see Mesothelioma Surgery - Biopsy.

In the laboratory, cells that are suspected to be cancerous are tested in two ways. First, they are viewed under a microscope to determine their general appearance. Second, they are tested for the presence of oncoproteins and other molecules that are produced by specific types of cancer cells.

When viewed under a microscope, mesothelioma cells and other types of cancer cells can be distinguished from normal healthy cells because of their shape and other differences in appearance. Further tests are needed to determine the exact nature of the cells. These tests evaluate the types of proteins that are present on the surface of the cells. When mesothelial cells become malignant, they begin to produce different types of proteins and some of these are present on the surface of the cells. Examining the types of surface proteins allows a histologist to determine if the cells are malignant mesothelioma, another type of cancer, or healthy cells.

Malignant Sarcomatoid Mesothelioma

In histological terms, there are four different types of mesothelioma: sarcomatoid, epithelial, biphasic, and desoplastic (a variant of sarcomatoid). Please see Epithelial and Biphasic for information on these other types of malignant mesothelioma cells.

Malignant sarcomatoid mesothelioma is the least common of the three cellular mesothelioma types. This form of mesothelioma accounts for approximately 10 to 15 percent of cases. When viewed under a microscope, malignant sarcomatoid mesothelioma cells appear as elongated spindle-shaped cells that are irregularly shaped and often overlap one another.

Desoplastic mesothelioma is considered a variant of sarcomatoid mesothelioma. This form is likely the most difficult of all mesotheliomas to diagnose. When desoplastic mesothelioma invades or metastasizes, the cells can appear very bland and can be misdiagnosed as benign fibrous tissue. Medical experts in mesothelioma say this form of mesothelioma should not be diagnosed with a needle core biopsy.

It's important to know that malignant sarcomatoid mesothelioma is sometimes difficult to diagnose on the basis of histological methods. For example, cells of another type of cancer called pulmonary sarcomatoid carcinoma are very similar in appearance (as well as other characteristics) to malignant sarcomatoid mesothelioma.

For this reason, if you are diagnosed with cancer and you know that you have been exposed to asbestos at some time in the past, obtaining a second diagnostic opinion may be important. Different types of cancer vary widely in terms of prognosis and treatment options, and if misdiagnosed, patients may not receive the most appropriate treatment for their cancer.

Prognosis and Treatment

Each of the four cellular forms of mesothelioma are generally treated in the same way. Treatment is not based on the specific type of cells involved, but instead on the location of tumors and the stage of the cancer. Please see Mesothelioma Treatment for more information about treatment options.

Each type of cancer responds to treatment very differently. In general, patients with malignant sarcomatoid mesothelioma have a poorer prognosis than patients with epithelioid mesothelioma, as sarcomatoid cancers are more aggressive and more resistant to treatment. Unfortunately, the general prognosis for all types of mesothelioma is usually poor, and the difference in prognosis between sarcomatoid, epithelioid, biphasic, and desoplastic cancers may amount to as little as only a few months.