Sarcomatoid mesothelioma is a much rarer form of the disease than epithelioid mesothelioma, comprising fifteen to twenty percent of all diagnosed cases. The generic term sarcoma refers to cancer originating from mesodermal or connective tissues in the body. Epithelial cells are also found in connective tissues; however the development of a sarcoma is more lethal than an epithelioid cancer. That said, mesothelioma is fatal in over ninety percent of all diagnoses. Malignant sarcomatoid mesothelioma cells originate in a different fashion than epithelial cancer cells, which are derived from the cells that make up the mesothelium, the membrane lining the chest and abdominal cavities as well as the heart and the lungs. Jump to sarcomatoid diagnosis, sarcomatoid prognosis, sarcomatoid life expectancy, sarcomatoid treatment, sarcomatoid symptoms.
Sarcomatoid mesothelioma is less likely to originate in the peritoneal or abdominal cavity. That does not mean, however, that other types of sarcoma malignancy are not common in the abdomen. The cell type is such that it is difficult to differentiate between sarcomatoid mesothelioma cells and cells of other types of sarcoma cancers found in the lungs and abdomen. In general, malignant sarcomatoid mesothelioma cells show more abnormality than their epithelioid counterparts, displaying a higher level of activity and aggressive behavior and under diagnostic study often display mitotic activity – that is, the processing of cell splitting and reproducing.
Diagnosing Sarcomatoid Mesothelioma
The challenge for the physician is determining whether sarcomatoid mesothelioma cells are in fact cancer of the mesothelium or represent some other sarcoma – a more common lung tumor or even melanoma. Sarcomatoid mesothelioma cells can easily be mistaken for sarcoma cells that are linked with not only lung tumors but organs in the peritoneal cavity.
Identifying the true source of the cancer may be a matter of diagnosing the mass itself. Pleural mesothelioma – cancer of the membrane around the lung – is relatively diffuse, spread across the surface of the mesothelium, rather than concentrated as in a tumor mass. Clues like this help the medical professional identify sarcomatoid mesothelioma as opposed to some other cancer. In the pleura alone, one researcher concluded that there are three types of tumors that can be related to sarcomatoid cells, each with a different etiology and each calling for its own form of treatment.
Malignant Sarcomatoid Mesothelioma Treatment
Sarcomatoid cells respond to different treatment choices than epithelial mesothelioma cells. Chemotherapy drugs that attack the proteins in an epithelioid cell may contain an enzyme that a sarcomatoid cell may resist. Treatment of malignant sarcomatoid mesothelioma is judged to be more difficult that epithelioid mesothelioma – in part, perhaps, because cases of pure sarcomatoid mesothelioma are relatively rare, resulting in a corresponding reduction in the availability of research material.
It is also true, however, that malignant sarcomatoid cells are more aggressive than the more common epithelioid cells. The cancer moves more rapidly and the prognosis is therefore somewhat poorer than for a patient with the more common mesothelioma variety which originates in the pleural mesothelium around the lungs and attached to the chest wall, with the slower moving epithelial cells as a catalyst.
It is more common to find sarcomatoid cells joined in combination with epithelioid mesothelioma cells in some fashion. This form of the disease is called biphasic mesothelioma, which is estimated to constitute 20% - 35% of all cases of the disease. Treatment of biphasic mesothelioma is complicated by the fact that a sarcomatoid malignancy will resist forms of treatment that are effective with epithelial cells, and vice versa.
In the case of one type, success may have been found in a chemotherapy drug that attacks proteins within the malignant cell. With a sarcoma, treatment may involve chemotherapy that results in cutting off the blood supply to the malignant cells or tumors, causing them to die. With biphasic mesothelioma, the treating physician may find it necessary to use treatment that includes procedures for both epithelioid and sarcomatoid cells. But the type of mesothelioma with the poorest survival rate after diagnosis continues to be sarcomatoid mesothelioma because of its aggressive and tenacious cell characteristics.
- Guidelines for Pathologic Diagnosis of Malignant Mesothelioma, Archives of Pathology and Laboratory Medicine, August 2009
- Differential Diagnosis of Sarcomatoid Mesothelioma from True Sarcoma…Pathology International, December 2006, Kushitani et al., http://www3.interscience.wiley.com/cgi-bin/fulltext/119414968/HTMLSTART
- Three Types of Spindle Cell Tumors of the Pleura: Fibroma, Sarcoma, and Sarcomatoid Mesothelioma, The American Journal of Surgical Pathology, October 1988, Carter et al.