Mesothelioma, the cancer most often caused by asbestos exposure, can be categorized by the location in the body where it originates: pleural, peritoneal, pericardial, and testicular mesotheliomas. It can also be categorized by the types of cells that make up most of the tumors: epithelial, sarcomatoid, or biphasic, a mixture of the two types. By this categorization epithelial mesothelioma is the most common type, making up as much as 70 percent of cases.
Epithelial mesothelioma is less aggressive than sarcomatoid mesothelioma. Although it is malignant and will spread and metastasize, it does so more slowly. This means that treatments for this type of mesothelioma are more hopeful and in some cases have a chance to be curative. Even so, this is still an aggressive type of cancer that usually comes with a poor prognosis and a reduced life expectancy.
Epithelial cells are found throughout the body. They make up the tissue that lines various parts of the body, including the skin and the lining of the throat, blood vessels, and organs. These cells act like a safety shield or a protective barrier. They are generally tightly packed together and may come in a variety of shapes depending on where they are in the body. They may be flat, cube shaped, or columnar.
When epithelial cells mutate, they may become cancerous and tend to lose any ordered shape. They become abnormal. When a mesothelioma tumor is mostly made up of these mutated epithelial cells, it is classified as epithelial or epithelioid mesothelioma. Pleural, peritoneal, pericardial, and testicular mesothelioma may all be epithelial. There are several subtypes of epithelial mesothelioma cells:
- Small cell. Small cell cancers are made up of small, uniform cells. These can easily be mistaken for the cells that make up small cell lung cancer.
- Adenomatoid. These cells are both epithelial and characteristic of cells that arise in the glands of the body.
- Tubulopapillary. This cell subtype makes a distinct pattern of papillary structures and small tubules.
- Deciduoid. This is a rare subtype of epithelial cells that are shaped like large polygons. It is easy to misdiagnose this type of mesothelioma because it is so rare.
- Solid. Solid cell types may be poorly- or well-differentiated. The well-differentiated type has round, orderly cells. In the poorly-differentiated type the cells are not well organized.
- Cystic. Cystic mesotheliomas are most common in the peritoneum and are often benign.
- Glomeruloid. These cells are round or oval-shaped and are not common in mesothelioma. It is thought that they are not related to asbestos exposure.
Diagnosis of Epithelial Mesothelioma
A diagnosis of epithelial mesothelioma may come after mesothelioma is diagnosed. This begins with a physical exam and imaging scans to determine that there is some type of unusual growth in the pleura or lungs. An imaging scan, like a CT scan, cannot tell a doctor if the cancer is lung cancer or mesothelioma or whether it is benign or malignant.
For a more specific diagnosis a biopsy must be done. This involves using a needle to remove a sample of tissue or fluid in most cases. If the suspected tumor is difficult to access, a surgical procedure may be needed to get a sample. The sample is then examined by a pathologist who will try to look at the physical appearance of the cells and how they are ordered to determine if they are mesothelial or lung cancer cells and then whether they are epithelial or sarcomatoid cells. If epithelial cells are found the pathologist will then try to determine which subtype they are. These distinctions are important for treatment.
A newer kind of diagnostic technique is making it easier for doctors and pathologists to diagnose mesothelioma and it cellular types and subtypes. The technique is called immunohistochemistry and it involves the use of antibodies to detect the antigens that are specific to each type of cancer cell. There are several of these antibodies that can be used to help diagnose epithelial mesothelioma.
Depending on the stage of the cancer and how much it has spread or metastasized, surgery may be a good treatment option. Epithelial mesothelioma is generally considered a resectable type of mesothelioma, meaning surgery can potentially remove all of the mass of the tumors that is visible. Sarcomatoid mesothelioma, on the other hand, is typically considered nonresectable.
For pleural epithelial mesothelioma, an extrapleural pneumonectomy, or EPP, is a possible treatment. It is an involved surgical procedure that removes the lung along with the pleura on the side of the chest where the cancer originated. This is typically only done when there is a hope for a cure and when the cancer has not yet spread to the lymph nodes. Patients must be in good general health for this complicated and risky surgery.
A less aggressive surgical strategy is called debulking, in which the surgeon removes as much of the tumor as possible. Surgery may also be done to remove the pleura on one side of the chest or to remove part of a lung. These surgeries are usually combined with chemotherapy and radiation for the best results. These treatments may be used before surgery to reduce the size of the tumor to be removed or after to eliminate any remaining cancer cells and reduce the chance that the patient will experience a recurrence.
One of the factors connected to better survival rates with mesothelioma is the epithelial cell type. Because these cells tend to adhere strongly to each other, they metastasize less readily than sarcomatoid cells. They will eventually metastasize if they are part of a malignant tumor, but will do so more slowly, giving a patient an overall better prognosis.
Other factors that affect prognosis include the age and gender of the patient, the patient’s general health, level of nutrition and degree of weight loss, ability to conduct normal everyday activities, and red blood cell, platelet, and white blood cell counts. Also important is the stage of the cancer at the time of diagnosis. The earlier the stage, the better the prognosis will be.
Getting an early diagnosis is important to having the best chance of survival from this or any type of mesothelioma. If you have been exposed to asbestos throughout your career you are at particular risk of developing epithelial mesothelioma and you should be screened regularly.
You should also be aware of symptoms and prepared to see your doctor if you have any signs that could indicate cancer. If you do get diagnosed with mesothelioma, there are legal avenues for you to seek compensation including lawsuits, settlements, and asbestos trust funds. A lawyer can help you decide which solution is best for your case.
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