Mesothelioma is a rare form of cancer in which malignant (cancerous) cells are found in mesothelium, protective sac that covers most of body's internal organs. Most people with mesothelioma work in jobs that inhale asbestos particles.

What is mesothelium?

Mesothelium is a membrane that covers and protects most of internal organs of body. It consists of two layers of cells: one layer directly surrounds organ and other forms a sac around organ. The mesothelium produces a lubricating fluid that is secreted between layers, allowing moving organs such as beating heart and expanding and contracting lungs to slide easily to adjacent structures.

Mesothelium has different names depending on where it is located in body. The peritoneum is a mesothelial tissue covering most of abdominal organs. The pleura is membrane that surrounds lungs and chest wall. The pericardium covers and protects heart. The mesothelial tissue surrounding male internal reproductive organs is called vaginal-testicular mesothelial tissue. The endometrium covers internal reproductive organs of a woman.

What is mesothelioma?

Mesothelioma is a disease in which mesothelial cells divide uncontrollably or randomly. They can penetrate and damage nearby tissues and organs. Cancer cells can also spread from their original location to other parts of body. Most mesothelioma begins in pleura or peritoneum.

Incidence of mesothelioma

Mesothelioma remains a relatively rare cancer, despite a reported increase in incidence over past 20 years. Approximately 2,000 new cases of mesothelioma are reported annually in United States. Mesothelioma is more common in men than women and increases with age, but disease can occur in men or at any age.

Risk factors for mesothelioma

Asbestos is a major risk factor for mesothelioma. In all cases, approximately 70% to 80% reported a history of exposure to asbestos at work. However, mesothelioma has been reported in some people not exposed to asbestos.

asbestos

Asbestos is name of a group of minerals that are naturally occurring masses of strong, soft fibers that can be separated into threads and weaves. Until 1970s, it sparked an industrial revolution, but was quickly abandoned when research linked it to cancer. Asbestos is widely used in many industrial products, including cement, brake pads, roof tiles, flooring, textiles, and insulation. If tiny particles of asbestos are in air, especially during production, they can be inhaled or swallowed, which can cause serious health problems. In addition to mesothelioma, asbestos exposure increases risk of lung cancer, asbestosis (a non-cancerous chronic lung disease) and other cancers such as throat and kidney cancer.

Asbestos has been mined and used commercially since late 19th century. Since early 1940s, millions of workers have been exposed to asbestos dust. Initially, risks associated with exposure to asbestos were unknown. However, it later emerged that shipyard workers, those who work in asbestos mines and factories, manufacturers of asbestos products, heating and construction workers, and other trade workers are at an increased risk of developing mesothelioma. Today, US Occupational Safety and Health Administration (OSHA) sets limits on acceptable asbestos exposure levels in workplace. Asbestos workers wear personal protective equipment to reduce risk of exposure.

The risk of asbestos-related illness increases with amount and duration of asbestos exposure. However, some people are only affected by mesothelioma for a short time. On the other hand, not all workers who are severely exposed to asbestos develop asbestos-related illnesses.

smoking

Smoking does not increase risk of developing mesothelioma. However, smoking and exposure to asbestos significantly increase risk of developing lung cancer.

Family history

There is evidence that household members and others living with asbestos workers are at increased risk of developing mesothelioma and possibly other asbestos-related diseases. This risk may result from exposure to asbestos dust from clothing and hair of asbestos workers. To reduce family members' exposure to asbestos fibers, asbestos workers often need to shower and change before leaving workplace.

Mesothelioma symptoms

Mesothelioma symptoms may not appear until 30 to 50 years after exposure to asbestos. Shortness of breath and chest pain due to pleural effusion are often symptoms of pleural mesothelioma. Symptoms of peritoneal mesothelioma include weight loss, abdominal pain, and bloating from fluid in abdomen. Other symptoms of peritoneal mesothelioma may include intestinal obstruction, bleeding disorders, anemia, and fever. If cancer has spread to other parts of body, symptoms may include pain, difficulty swallowing, and swelling of neck or face.

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

Diagnosis of mesothelioma

Diagnosis of mesothelioma is often difficult because symptoms resemble some other diseases. Diagnosis begins with a review of patient's medical history, including any history of asbestos exposure. A complete physical examination may be done, including a chest or abdominal x-ray and lung function tests. CT (or computed tomography) or MRI may also be helpful. A CT scan is a series of detailed images of areas inside body taken by a computer connected to an X-ray machine. In an MRI, a powerful magnet connected to a computer is used to take detailed images of areas inside body. Pictures can be viewed on monitor or printed.

A biopsy is required to confirm diagnosis of mesothelioma. During a biopsy, a surgeon or medical oncologist (a doctor who specializes in diagnosing and treating cancer) takes a sample of tissue for examination by a pathologist under a microscope. A biopsy can be taken in different ways, depending on location of abnormal area. If cancer is in chest, doctors may do a thoracoscopy. During this procedure, doctors make a small incision in chest wall and insert a thin, bright tube called a thoracoscope into chest between two ribs. Thoracoscopy allows doctor to examine chest and obtain tissue samples. If cancer is in abdomen, doctors may perform a laparoscopy. To examine tissue, doctor makes a small hole in abdomen and inserts a special instrument called a laparoscope into abdomen. If these procedures do not produce enough tissue, more extensive exploratory surgery may be needed.

mesothelioma staging

If mesothelioma is diagnosed, your doctor will want to know stage (or grade) of disease. Staging involves additional tests to carefully try to figure out if cancer has spread, and if so, to what part of body. Knowing stage of disease helps doctors plan treatment.

See Mesothelioma staging system.

Mesothelioma is considered localized if tumor is found only on surface of membrane from which it originated. It is classified as progressive if it has spread to other parts of body such as lymph nodes, lungs, chest wall, or abdominal organs.

Treatment of mesothelioma

Treatment for mesothelioma depends on location of cancer, stage of disease, person's age, and overall health. Standard treatment options include surgery, radiation therapy, and chemotherapy. Sometimes these treatments are combined.

Surgery is a common treatment for mesothelioma. Doctors may remove part of lining of chest or abdomen and some of surrounding tissue. For cancer of pleura (pleural mesothelioma), lung may be removed using a procedure called pneumonectomy. Sometimes part of diaphragm, muscle under lungs that helps with breathing, is also removed.

Radiation therapy, also called radiotherapy, uses high-energy rays to kill cancer cells and shrink tumors. Radiation therapy only affects cancer cells in area being treated. The radiation may come from machine (external radiation) or emitting material may be placed through a thin plastic tube into area where cancer cells are found (internal radiation therapy).

Chemotherapy is use of anticancer drugs to kill cancer cells throughout body. Most of medicines used to treat mesothelioma are given by injection into a vein (intravenously or intravenously). Doctors are also studying effects of giving chemotherapy drugs directly into chest or abdomen (intracavitary chemotherapy).

To relieve symptoms and relieve pain, doctors may use a needle or thin tube to drain fluid that has accumulated in chest or abdomen. The procedure for removing fluid from chest is called thoracocentesis. The removal of fluid from abdominal cavity is called a puncture. The drug can be given through a tube into chest cavity to prevent more fluid from accumulating. Radiation therapy and surgery can also relieve symptoms.

Current research

Because mesothelioma is so difficult to control, National Cancer Institute (NCI) sponsors clinical trials (studies conducted on humans) to find new treatments and better ways to use existing treatments. Before recommending any new treatment for general use, clinicians conduct clinical trials to determine whether treatment is safe for patient and effective for disease. Participation in clinical trials is an important treatment option for many people with mesothelioma.