Mesothelioma Basics

What is Mesothelioma? Mesothelioma is a rare form of malignant cancer of the mesothelium. Early in the development of an embryo, 3 initial layers of cells exist, the ectoderm, the mesoderm and the endoderm. The mesothelium derives embryonically from the mesodermal cell layer and lines various organs and cavities. One mesothelial layer lines individual organs (visceral) while the other layer lines the cavity wall (parietal). Combined, these layers help to protect moving internal organs by secreting lubricant that decreases frictional force.

Who gets Mesothelioma? Mesothelioma, by definition, can occur wherever there is mesothelium. This includes the visceral mesothelium lining various organs such as the lungs, the heart, the kidneys, etc. Also included is the parietal mesothelium lining the body cavities such as the pleura, the peritoneum, the pericardium, etc. For the most part however, mesothelioma is rare and is strongly associated with cancer of the pleura (mesothelium lining the lungs) due to asbestos exposure.

About 2,000-3,000 new cases of mesothelioma are diagnosed each year in the United States. Internationally, the incidence rate is harder to measure since many non-industrialized countries may not keep records of mesothelioma registries. Generally, more men develop mesothelioma possibly due to a greater exposure rate to asbestos. On the average, it takes about 35-40 years after initial exposure to asbestos to develop mesothelioma. This may explain why this cancer develops mostly in the age range of 50-70. This is not a hard and fast rule as mesothelioma has been known to affect people of all ages, genders and race.

What are the symptoms? Symptoms of mesothelioma may not appear until 30 to 50 years after exposure to asbestos. Shortness of breath and pain in the chest due to an accumulation of fluid in the pleura are often symptoms of pleural mesothelioma. Other symptoms include cough, weight loss, weakness and increased sputum production. Symptoms of peritoneal mesothelioma include weight loss and abdominal pain and swelling due to a buildup of fluid in the abdomen. Other symptoms of peritoneal mesothelioma may include bowel obstruction, blood clotting abnormalities, anemia, and fever. If the cancer has spread beyond the mesothelium to other parts of the body, symptoms may include pain, trouble swallowing, or swelling of the neck or face.

These symptoms may be caused by mesothelioma or by other, less serious conditions. It is important to see a doctor about any of these symptoms. Only a physician can make a diagnosis.

What types of Mesothelioma are there?

There are 3 pathologic types of mesothelioma: Epithelioid, Sarcomatoid and Mixed.

• Epithelioid. The epithelioid variety of mesothelioma is the most common and has a better survival time. Often mistaken for adenocarcinoma (another type of cancer associated with the lining of the body walls and glandular tissue), your physician may need to refer to a pathologist for special staining techniques to differentiate between the two diseases. Since treatment options and mean survival rates differ between mesothelioma and adenocarcinoma, care must be taken to avoid misdiagnosing these disease. A careful history of the illness (elucidating past exposure to asbestos) and full a physical examination are often crucial.
• Sarcomatoid. These mesotheliomas are the most rare and resemble true sarcomas (cancers that arise from or resemble supportive tissues such as fat, bone, muscles, blood vessels, cartilage and sometimes deep skin). The mean survival time for this variety is worse.
• Mixed. These mesotheliomas have both epithelioid and sarcomatoid features.

Pleural mesotheliomas usually begin at the lower parts of the chest wall and progress along lymphatics to access surrounding areas. The initial stages may be that of discrete plaques and nodules that come together to form large densities of malignant tissue.

Treatment Options	Diagnosis