Types of Mesothelioma

Mesothelioma is caused by long-term, repeated exposure to asbestos fibers. The disease is generally found in four different forms: pleural, peritoneal, pericardial, and testicular. In each case, the cancer develops in mesothelial cells, which form the membranous linings that surround and protect organs. The different names for each type of mesothelioma refer to the point of origin of the cancer.

Mesothelial membranes are made up of two different layers, called the parietal and visceral layers. Parietal layers are outer layers, and these typically cover large areas such as the chest cavity (in the case of pleural and pericardial membranes) and the abdominal cavity (as in the case of peritoneal membranes). Visceral layers are those that cover organs such as the lungs and heart. Mesothelioma develops in these membranes when asbestos fibers become trapped in the spaces between mesothelial cells.

Mesothelioma is a particularly aggressive type of asbestos cancer, and is highly resistant to treatment, resulting in very high mortality rates and poor prognosis for people diagnosed with the disease. In general, pleural mesothelioma responds more positively to treatment, particularly if the disease is diagnosed early. However, all forms of mesothelioma are difficult to diagnose, and unfortunately, it is common for the disease to be diagnosed too late for treatment to be effective.

Pleural Mesothelioma

Pleural mesothelioma develops in the mesothelial lining of the lungs, which is known as the pleura. About 75 percent of all mesothelioma cases are pleural.

Symptoms of pleural mesothelioma include difficulty swallowing, a persistent dry cough, persistent chest pain, or pain when breathing, and difficulty breathing even when resting. These mesothelioma symptoms result from pressure on the lungs and respiratory system, caused by thickening of the pleural membrane and fluid build-up between membrane layers. As the cancer advances, lumps may develop under the skin of the chest.

Diagnosis of pleural mesothelioma involves imaging tests such as chest x-rays, MRIs, and CT scans, and may also include biopsies that remove tissue and fluid to test for the presence of cancer cells. These tests also help determine the stage of the cancer and the options available for treatment. Generally, patients in stage one and two mesothelioma are good candidates for surgery, whereas patients in stages three and four have more limited treatment options, and may only be able to receive palliative treatments.

Peritoneal Mesothelioma

Peritoneal mesothelioma develops in the peritoneal lining of the abdominal cavity. This is a relatively rare form of mesothelioma; approximately 10 to 20 percent of all mesothelioma cases are peritoneal in nature.

Symptoms of peritoneal mesothelioma include pain or swelling of the abdomen, changes in bowel habits (such as constipation or diarrhea), unexplained weight loss, and nausea or vomiting. These symptoms are caused by thickening of peritoneal membranes and fluid build-up, which puts pressure on internal organs and prevents normal function of some organs. As the cancer advances, people with peritoneal mesothelioma may notice lumps developing under the skin of the abdomen.

Diagnosis of peritoneal mesothelioma involves imaging tests such as CT scans and MRIs, as well as biopsies of fluid and tissue to detect the presence of mesothelioma cells. There is currently no recognized staging process for peritoneal mesothelioma.

Peritoneal mesothelioma is problematic in terms of treatment, because the cancer can spread quickly throughout the peritoneum and often metastasizes more quickly than other types of mesothelioma. In some cases surgery is possible, but this is typically a palliative treatment option.

Pericardial Mesothelioma

Pericardial mesothelioma develops in the membrane that surrounds the heart, also known as the pericardium. This is a very rare form of mesothelioma, occurring in only 1 to 5 percent of cases. This form of mesothelioma is also very difficult to treat.

Symptoms of pericardial mesothelioma include irregular heartbeat or palpitations, chest pain, and difficulty breathing. These are caused by the pressure put on the heart by the build-up of fluid in the spaces between pericardial membrane layers.

It is very rare for pericardial mesothelioma to be diagnosed early enough for any form of treatment to be effective, and pericardial mesothelioma patients typically have an extremely poor prognosis. In very rare cases, the cancer may be diagnosed early enough for surgery to have a positive effect; however, the proximity of this cancer to the heart makes such surgery a high-risk mesothelioma treatment option.

Testicular Mesothelioma

Testicular mesothelioma is the rarest of all mesothelioma cancers, as less than one hundred cases have been recorded. This type of mesothelioma develops in the lining that surrounds the testicles, known as the tunica vaginalis.

Due to the extreme rarity of testicular mesothelioma, very little has been noted about its symptoms and the treatment options available. Often, the disease is not diagnosed until patients notice the appearance of testicular lumps. In some cases, surgery for an unrelated condition such as a hernia leads to the detection of testicular mesothelioma.

If the primary tumor has developed in the testicles, treatment involves removal of part or the entire affected testicle, followed by chemotherapy or radiation therapy. In many cases the testicular tumor is secondary, and the primary cancer is located in the peritoneum. In these cases, treatment follows established patterns for peritoneal mesothelioma in addition to removal of testicular tumors.