Mesothelioma---Definition---Description---etc

Definition

Mesothelioma is a rare form of cancer. In mesothelioma, malignant cells are found in the sac lining of the chest (the pleura) or the abdomen (the peritoneum). The majority of people with mesothelioma have a history of jobs that exposed them to asbestos, an insulation material.

Description

In the chest and abdominal cavities, as well as in the cavity around the heart (pericardial sac), there is a layer of specialized cells called mesothelial cells. These cells also surround the outer surface of most internal organs. These cells form tissue called mesothelium.

The mesothelium performs a protective function for the internal organs by producing a lubricating fluid that permits the organs to move around. For example, this fluid makes it easier for the lungs to move inside the chest while a person breathes. The mesothelium of the abdomen is known as the peritoneum, and the mesothelium of the chest is called the pleura. The pericardium refers to the mesothelium of the pericardial cavity.

There are three primary types of malignant mesotheliomas:

• Epithelioid. About 50% to 70% of mesotheliomas are of this type and have the best outlook for survival.
• Sarcomatoid. Approximately 7% to 20% of cases are of this type.
• Mixed/biphasic. From 20% to 35% of mesothelioma cases fall into this category.

Approximately three-fourths of all mesotheliomas begin in the chest cavity and are known as pleural mesotheliomas. Peritoneal mesotheliomas begin in the abdomen, and make up around 10% to 20% of all cases. Mesotheliomas arising in the cavity around the heart are quite rare.

Demographics

Mesothelioma is a fairly rare form of cancer. According to the American Cancer Society, there are an estimated 2,000 to 3,000 new cases per year of the disease in the United States, but this figure seems to be rising. This rising figure is related to the widespread use of asbestos from the 1940s to the end of the 1970s. European researchers studying the disease expect deaths from mesothelioma to peak around the year 2020 and then drop off, because asbestos use has been cut back greatly since the early 1980s.

The average age of a person with mesothelioma is 50 to 70 years old. It affects men three to five times more often than women and is less common in African-Americans than in Caucasian Americans.

Causes and Symptoms

The primary risk factor for developing mesothelioma is asbestos exposure. In the past, asbestos was used as a very effective type of insulation. The use of this material, however, has been declining since the link between asbestos and mesothelioma has become known. It is thought that when the fibers of asbestos are inhaled, some of them reach the ends of the small airways and penetrate into the pleural lining. There the fibers may directly harm mesothelial cells and eventually cause mesothelioma. If the fibers are swallowed, they can reach the abdominal cavity, where they can contribute to the formation of peritoneal mesothelioma.

Exposure to certain types of radiation as well as to a chemical related to asbestos known as zeolite has also been related to incidences of mesothelioma.

The early symptoms of mesothelioma are often ignored, because they may be caused by a variety of ailments. These symptoms include:

• pain in the lower back or at the side of the chest
• shortness of breath
• difficulty swallowing
• cough
• fever
• fatigue
• abdominal pain, weight loss, and nausea and vomiting (symptoms of peritoneal mesothelioma)