Mesothelioma is an uncommon type of cancer in which the malignant (cancerous) cells are found in the mesothelium, a protective sac lining most of the body's internal organs.
Most people who develop the disease were exposed to asbestos inhalation at their place of work.
The mesothelium is a membrane that covers and protects most of the internal organs of the body. It is composed of two layers of cells: One layer immediately surrounds the organ {the visceral layer} and the other layer forms a sac around it {the parietal layer}.
The mesothelium produces a lubricating fluid that is released between these layers, allowing moving organs (such as the beating heart and the expanding and contracting lungs) to glide easily against surrounding structures.
The mesothelium has different names, depending on its location in the body. The peritoneum is the mesothelial lining that covers most of the organs in the abdominal cavity. The pleura is the lining that surrounds the lungs and lines the wall of the chest cavity. The pericardium covers and protects the heart. The mesothelial tissue surrounding the male internal reproductive organs is called the tunica vaginalis testis. The tunica serosa uteri covers the internal reproductive organs in women.
Mesothelioma (cancer of the mesothelium) is a disease in which cells of the mesothelium become abnormal and divide without control or order. They can invade and damage nearby tissues and organs. Cancer cells can also metastasize (spread) from their original site to other parts of the body. Most cases of the cancer begin in the pleura or peritoneum.
How common is mesothelioma?
Although reported incidence rates have increased in the past 20 years, this disease is still a relatively uncommon type of cancer. About 2,000 new cases of mesothelioma are diagnosed in the United States each year. It occurs more often in men than in women and risk increases with age, but this disease can appear in either men or women at any age.
What are the risk factors?
Working with asbestos is the major risk factor for mesothelioma. A history of asbestos exposure at work is reported in about 70 percent to 80 percent of all cases. However, the disease has also been reported in some individuals without any known exposure to asbestos.
Asbestos is the name of a group of minerals that occur naturally as masses of strong, flexible fibers that can be separated into thin threads and woven. Asbestos has been widely used in many industrial products, including cement, brake linings, roof shingles, flooring products, textiles, and insulation. If tiny asbestos particles float in the air, especially during the manufacturing process, they may be inhaled or swallowed, and can cause serious health problems.
Apart from causing mesothelioma, exposure to asbestos increases the risk of lung cancer, asbestosis (a non cancerous, long standing chronic lung ailment), and other cancers, such as those of the larynx and kidney.
Smoking does not appear to increase the risk of mesothelioma.
However, the combination of smoking and asbestos exposure significantly increases a person's risk of developing cancer of the air passageways in the long run.
Who are the people at risk of developing the cancer?
Asbestos has been mined and used commercially since the late 1800s. Its use greatly increased during World War II. Since the early 1940s, millions of American workers have been exposed to asbestos dust. Initially, the risks associated with asbestos exposure were not known.
However, an increased risk of developing mesothelioma was later found among shipyard workers, people who work in asbestos mines and mills, producers of asbestos products, workers in the heating and construction industries, and other tradespeople.
Today, the U.S. Occupational Safety and Health Administration (OSHA) sets limits for acceptable levels of asbestos exposure in the workplace. People who work with asbestos wear personal protective equipment to lower their risk of exposure.
The risk of asbestos-related disease increases with heavier exposure to asbestos and longer exposure time. However, some individuals with only brief exposures have developed this type of cancer. On the other hand, not all workers who are heavily exposed develop asbestos-related diseases.
There is some evidence that family members and others living with asbestos workers have an increased risk of developing this cancer, and possibly other asbestos-related diseases. This risk may be the result of exposure to asbestos dust brought home on the clothing and hair of asbestos workers.
To reduce the chance of exposing family members to asbestos fibers, asbestos workers are usually required to shower and change their clothing before leaving the workplace.
Symptoms
Symptoms 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.
Symptoms of peritoneal mesothelioma include weight loss and abdominal pain and swelling due to a build up of fluid in the abdomen.
Other symptoms of peritoneal mesothelioma may include intestinal obstruction, blood clotting abnormalities, low blood levels{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 doctor can make a definitive diagnosis.
How is the diagnosis made?
Diagnosing mesothelioma is often difficult, because the symptoms are similar to those of a number of other conditions. Diagnosis begins with a review of the patient's medical history, including any history of asbestos exposure.
A complete physical examination must be done , x-rays of the chest or abdomen and lung function tests. A CT (or CAT) scan or an MRI can also be ordered for. A CT Scan is a series of detailed pictures of areas inside the body created by a computer linked to an x-ray machine.
In an MRI, a powerful magnet linked to a computer is used to make detailed pictures of areas inside the body. These pictures are viewed on a monitor and can also be printed.
To confirm a diagnosis, a biopsy must be done. Biopsy involves the removal of a sample of the cancerous tissue for examination in the laboratory by a surgeon or medical oncologist{a doctor who is a specialist in diagnosing cancer}. The sample is examined in the laboratory by a pathologist{ a medical specialist in examining cells}. A biopsy may be done in different ways, depending on where the abnormal area is located.
If the cancer is in the chest, the doctor may perform a thoracoscopy. In this procedure, the doctor makes a small cut through the chest and puts a thin, lighted tube called a thoracoscope into the chest between two ribs. Thoracoscopy allows the doctor to look inside the chest and obtain tissue samples. If the cancer is in the abdomen, the doctor may perform a peritoneoscopy.
To obtain tissue for examination, the doctor makes a small opening in the abdomen and inserts a special instrument called a peritoneoscope into the abdominal cavity. If these procedures do not yield enough tissue, more extensive diagnostic surgery may be necessary.
If the diagnosis is mesothelioma, the doctor will want to learn the stage (or extent) of the disease. Staging involves more tests in a careful attempt to find out whether the cancer has spread and, if so, to which parts of the body. Knowing the stage of the disease helps the doctor plan treatment.
The cancer is localized if the cancer is found only on the membrane surface where it originated. It is classified as advanced if it has spread beyond the original membrane surface to other parts of the body, such as the lymph nodes, lungs, chest wall, or abdominal organs.
