Mesothelioma is a rare form of cancer, which most commonly affect the covering of the lungs and chest wall. Mesothelioma can also develop in other areas like the coverings of the intestine, or heart. Mesothelioma most commonly results from previous exposure to asbestos. Most people who develop mesothelioma have worked on jobs where they inhaled asbestos particles.
What is the mesothelium?
The mesothelium is a layer of tissue 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 other forms a sac around it. 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 adjacent structures. Mesothelium covers the external surfaces of the heart and lung. It also covers the inner surface of the chest wall and the inner surface of the sac that surrounds the heart called pericardium.
The mesothelium has different names, depending on its location in the body. The peritoneum is the mesothelial tissue that covers most of the organs in the abdominal cavity. The pleura is a membrane 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.
What is mesothelioma?
Mesothelioma (cancer of the mesothelium) is basically cancer arising from the mesothelial cells. It can occur in most parts where the mesothelial cells are located including lungs, chest wall, pericardium, and outer surfaces of the intestine. In mesotheliioma the 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 mesothelioma begin in the pleura or peritoneum.
How common is mesothelioma?
Although reported incidence rates have increased in the past 20 years, mesothelioma is still a relatively rare cancer. About 3,000 new cases of mesothelioma are diagnosed in the United States each year. Mesothelioma 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. Read epidemiology of mesothelioma for more details on this topic.
What are the risk factors for mesothelioma?
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, mesothelioma has been reported in some individuals without any known exposure to asbestos. History of exposure to various other chemicals have been found in some of these patients, but majority of these patients have no understandable risk factors for mesothelioma.
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. In addition to mesothelioma, exposure to asbestos increases the risk of lung cancer, asbestosis (a non-cancerous, 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 lung cancer and cancers of many other areas of the body including the air passage areas. Read about risk factors for the development of mesothelioma.
Who is at increased risk for developing mesothelioma?
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 mesothelioma. 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 mesothelioma, 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.
To read more this topic click on this link: who is at increased risk of developing mesothelioma?
What are the symptoms of mesothelioma?
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 the most common symptoms of pleural mesothelioma. 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 are not specific to mesohelioma and these symptoms may also be caused by other, less serious conditions. If you develop any of these symptoms it is important to see a doctor about any of these symptoms. Read more about symptoms of mesothelioma in the sections on natural history and clinical features of mesothelioma.
How is mesothelioma diagnosed?
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 may be performed, including x-rays of the chest or abdomen and lung function tests. A CT (or CAT) scan or an MRI may also be useful. 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.
A biopsy is needed to confirm a diagnosis of mesothelioma. A surgeon or a radiologist could remove a piece of the pleura or suspected tissue. Radiologist has the advantage of doing a biopsy under CT scan visualization. A pathologist will study the removed tissue under a microscope. A surgeon may do a biopsy 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 wall 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.
Mesothelioma is described as 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. Read more about diagnosis in the section on diagnosis of mesothelioma
How is mesothelioma treated?
Treatment for mesothelioma depends on the location of the cancer, the stage of the disease, and the patient's age and general health. Standard treatment options include surgery, radiation therapy, and chemotherapy. Sometimes, these treatments are combined.
Surgery for mesothelioma
Surgery is a common treatment for mesothelioma. The doctor may remove part of the lining of the chest or abdomen and some of the tissue around it. For cancer of the pleura (pleural mesothelioma), a lung may be removed in an operation called a pneumonectomy. Sometimes part of the diaphragm, the muscle below the lungs that helps with breathing, is also removed. Read more on surgical treatment of malignant mesothelioma.
Radiation therapy for mesothelioma
Radiation therapy, also called radiotherapy, involves the use of high-energy rays to kill cancer cells and shrink tumors. Unlike chemotherapy (see below) radiation therapy affects the cancer cells only in the treated area. The radiation may come from a machine (external radiation) or from putting materials that produce radiation through thin plastic tubes into the area where the cancer cells are found (internal radiation therapy). Read more on radiation therapy of mesothelioma
Chemotherapy for mesothelioma
Chemotherapy is the use of chemical substances to kill cancer cells. Fast growing cancer cells are more vulnerable to chemotherapy drugs than the normal cells. Chemotherapy will be intermittent rather than continuous like radiation therapy. During the rest period your normal cells recover from the bad effects of chemotherapy but the cancer cells may not recover from the damage. Most drugs used to treat mesothelioma are given by injection into a vein (intravenous, or IV). Sometimes chemotherapy is put directly in to the pleural cavity. This is done to have local control of the disease. Good results have been achieved with pleural cavity treatment using chemotherapy or radioactive drugs. To relieve symptoms and control pain, the doctor may use a needle or a thin tube to drain fluid that has built up in the chest or abdomen. The procedure for removing fluid from the chest is called thoracentesis. Removal of fluid from the abdomen is called paracentesis. Drugs may be given through a tube in the chest to prevent more fluid from accumulating. Radiation therapy and surgery may also be helpful in relieving symptoms. Read more about chemotherapy of mesothelioma.
Are new treatments for mesothelioma being studied?
Yes. Because mesothelioma is very hard to control, researchers are always working on newer and newer forms of treatment for this disease. The National Cancer Institute and many other organizations are actively engaged in finding new treatments for mesothelioma. Before any new treatment can be recommended for general use, doctors conduct clinical trials to find out whether the treatment is safe for patients and effective against the disease. Participation in clinical trials is an important treatment option for many patients with mesothelioma. New treatment options like gene therapy is being tried in the treatment of mesothelioma.
How can I participate in a mesothelioma clinical trial?
People interested in taking part in a mesothelioma clinical trial should initially talk with their doctor. Information about clinical trials is available bt calling at 1-800-4-CANCER. If you call this number information specialists will provide you with detailed information about specific ongoing clinical trials. You may also search the National Cancer Institute website for clinical trials site to get updated information on ongoing clinical trials.