Mesothelioma is most commonly caused by exposure to asbestos.
A mesothelioma is a tumor of the mesothelium, a protective membrane that lines many internal cavities, including those of the lungs, abdomen and heart. This relatively rare tumor occurs five times more frequently in males, and the risk of developing the tumor increases with age. In fact, three-fourths of mesothelioma patients are diagnosed after age 65. The cancer usually begins as a group of individual plaques that grow and coalesce into a sheet-like tumor that covers the affected organs.
Mesotheliomas in the lung cavity, known as pleural mesotheliomas, are the most common form of the cancer. They usually begin in the lower chest and sometimes spread to the diaphragm, where they can cover the lung surface. They may also extend into other areas such as the ribs, throat and spine as they progress. According to the American Cancer Society, although some mesotheliomas are benign, malignant mesotheliomas are almost always fatal, with the 5-year-survival-rate being about 10 percent.
The most common cause of mesothelioma appears to be exposure to asbestos, particularly the inhalation of its fibers. Although most manufacturing with asbestos ceased in 1989, older products still contain asbestos. Many patients with mesothelioma were exposed to asbestos while installing insulation; however, miners, factory workers, construction workers, railroad workers and ship builders were other occupations at risk for exposure. Studies show that people living with these workers also risk developing mesothelioma through secondary exposure. Additionally, someone who lives, works or attends school in a building with asbestos is at risk for developing mesothelioma.
The first sign of pleural mesothelioma is usually chronic chest pain, similar to viral pneumonia or lung cancer. Other symptoms include chronic coughing, shortness of breath and weight loss. Peritoneal mesothelioma is caused by swallowing asbestos fibers and affects the abdominal cavity. The symptoms of this less common type of malignant mesothelioma include abdominal pain and swelling, bowel obstruction and weight loss. Pericardial mesothelioma affects the heart cavity and is quite rare. Someone with this type of cancer may experience chest pain, heart palpitations, coughing and difficulty breathing. Mesothelioma of the tunica vaginalis is also a rare form that may appear as mass on a testicle.
A chest x-ray, computed tomography (CT) scan or magnetic resonance imaging (MRI) scan can determine the location of the cancer and how much it has spread. If there is fluid in the chest or abdomen, the doctor may insert a needle to remove a sample that can be tested for the presence of cancer cells. Sometimes it is hard to differentiate mesothelioma from other types of cancers using these methods.
If other tests indicate cancer, the doctor will perform a biopsy. The less invasive thoracoscopy only requires a small incision between the ribs that allows the doctor to insert a tube with a video camera and remove the tissue sample. A similar procedure, called a laparoscopy, can be performed to obtain a tissue sample from the abdomen. If a larger sample is needed, the doctor must open the chest or the abdomen.
Surgery is usually the primary treatment and may be effective by itself if the tumor is confined to the lung cavity. The extrapleural pneumonectomy is removal of the lung, while pleurectomy with decortication removes only the lining in the lung. Both of these procedures have a risk of disease recurrence; however, the pleurectomy with decortication allows a higher quality of life. Sometimes surgery is performed to remove excess fluid and make it easier for the patient to breathe.
According to the National Cancer Institute, doctors sometimes treat mesothelioma with an extrapleural pneumonectomy followed by chemotherapy and then radiotherapy to prevent recurrence. Chemotherapy may also be used before surgery to shrink the cancer. A higher dose of chemotherapy can be used when it is injected directly into the chest or abdomen cavity. Radiation therapy directs energy rays at a particular cancerous area; therefore, its not effective on cancer that has spread to other parts of the body. In addition to eradicating cancer, radiation therapy may be used to alleviate chest pain and breathing difficulty.
Avoiding exposure to asbestos at work or in older homes is the most effective way to prevent mesothelioma. According to the Mayo Clinic, it's important to follow an employers safety regulations when working in an environment that might contain asbestos. Employees should wear protective equipment while working, and then shower and change clothes after work to prevent contamination. When renovating an older home that may contain insulation or other products with asbestos, it is best to hire professionals that are trained in asbestos removal. Individuals concerned about asbestos exposure should also talk to their doctors about precautions they can take.