Malignant mesothelioma (me-zo-thee-le-O-muh) is a rare cancer that occurs in the thin layer of tissue that covers the majority of your internal organs (mesothelium).
Doctors divide mesothelioma into different types based on what part of the mesothelium is affected, including:
- Pleural malignant mesothelioma, which affects the tissue that surrounds the lungs and is the most common form of mesothelioma.
- Peritoneal mesothelioma, which occurs in the tissue in your abdomen.
- Pericardial mesothelioma, which affects the tissue surrounding the heart.
- Mesothelioma of the tunica vaginalis, which occurs in the lining around the testicles.
Signs and symptoms of mesothelioma vary depending on where the cancer occurs.
Pleural mesothelioma signs and symptoms may include:
- Shortness of breath
- Painful breathing (pleurisy)
- Painful coughing
- Chest pain under the rib cage
- Unusual lumps of tissue under the skin on your chest
- Unexplained weight loss
- Dry (nonproductive) cough
Peritoneal mesothelioma signs and symptoms may include:
- Abdominal pain
- Abdominal swelling
- A change in your bowel habits, such as more frequent diarrhea or constipation
- Lumps of tissue in the abdomen
- Unexplained weight loss
Signs and symptoms of pericardial mesothelioma and mesothelioma of the tunica vaginalis are unclear. These forms are so rare that not much information is available. Pericardial mesothelioma signs and symptoms may include difficulty breathing or chest pains. Mesothelioma of the tunica vaginalis may be first detected as a mass on a testicle.
In general, cancer begins when a series of genetic mutations occur within a cell, causing the cell to grow and multiply out of control, when healthy cells would normally die. The accumulating abnormal cells form a mass (tumor). Cancer cells invade nearby tissues and can break off from an initial tumor to spread elsewhere in the body (metastasize). It isn’t clear what causes the initial genetic mutations that lead to mesothelioma, though researchers have identified factors that may increase the risk. It’s likely that cancers form because of an interaction between many factors, such as inherited conditions, your environment, your health conditions and your lifestyle choices.
A form of noncancerous (benign) tumor that can occur in the chest is sometimes called benign mesothelioma. However, this name is misleading. Benign mesothelioma doesn’t begin in the same cells where the cancerous forms of mesothelioma begin. And, in a minority of cases, benign mesothelioma can be very aggressive, despite the term “benign.” For this reason, some doctors now refer this tumor as solitary fibrous tumor. Solitary fibrous tumor usually doesn’t cause signs and symptoms. Most cases are inadvertently discovered during tests and procedures for other conditions. It isn’t clear what causes solitary fibrous tumors, but they aren’t linked to asbestos exposure.
People who work around asbestos fibers are thought to have the greatest risk of mesothelioma. When asbestos is broken up, such as during the mining process or when removing asbestos insulation, dust may be created. If the dust is inhaled or swallowed, the asbestos fibers may settle in the lungs or in the stomach, where they can cause irritation that may lead to mesothelioma, though how exactly this happens isn’t understood. Mesothelioma risk is believed to be increased in people who are exposed to high levels of asbestos, in people who are exposed to asbestos over a long period of time and in people exposed to asbestos at a young age. It can take 30 to 40 years or more for mesothelioma to develop as a result of asbestos exposure. Some people with years of asbestos exposure never develop mesothelioma. And yet, others with very brief exposure develop the disease. This indicates that other factors may be involved in determining whether someone gets mesothelioma or doesn’t. For instance, you could inherit a predisposition to cancer or some other condition could increase your risk.
Factors that may increase the risk of mesothelioma include:
- Personal history of asbestos exposure. If you’ve been directly exposed to asbestos fibers at work or at home, your risk of mesothelioma is greatly increased.
- Living with someone who works with asbestos. People who are exposed to asbestos may carry the fibers home on their skin and clothing. These stray fibers can put others in the home at risk of mesothelioma. People who work with asbestos should shower and change clothes before leaving work.
- Smoking. Risk of mesothelioma is increased greatly in smokers who are exposed to asbestos.
- SV40. Some research indicates a link between mesothelioma and simian virus 40 (SV40), a virus originally found in monkeys. Millions of people may have been exposed to SV40 when receiving polio vaccinations between 1955 and 1963, because the vaccine was developed using monkey cells. Once it was discovered that SV40 was linked to certain cancers, the virus was removed from the polio vaccine. Whether SV40 increases the risk of mesothelioma is a point of debate, and more research is needed.
- Radiation. Some research links mesothelioma to the radioactive substance thorium dioxide, which was used along with X-rays to diagnose various health conditions from the 1920s to the 1950s. Thorium dioxide was later found to cause cancer and is no longer used.
- Family history. A family history of mesothelioma may increase your risk of mesothelioma, but more research is needed to understand this theory.
As pleural mesothelioma spreads in the chest, it puts pressure on the structures in that area. This can cause complications, such as:
- Difficulty breathing
- Chest pain
- Difficulty swallowing
- Swelling caused by pressure on the large vein that leads from your upper body to your heart (superior vena cava syndrome)
- Pain caused by pressure on the nerves and spinal cord
- Accumulation of fluid in the chest (pleural effusion), which can compress the lung nearby and make breathing difficult
People who die of mesothelioma usually die from related complications, such as lung failure, heart problems, stroke and other causes.
If you have signs and symptoms that might indicate mesothelioma, your doctor will conduct a physical exam to check for any lumps or other unusual signs. Your doctor may order imaging scans, such as a chest X-ray or a computerized tomography (CT) scan of your chest or abdomen, to look for abnormalities. It’s not uncommon for mesothelioma to be misdiagnosed initially because mesothelioma is rare, and its signs and symptoms aren’t specific. Your doctor will likely rule out other more common conditions before considering mesothelioma.
Biopsy, a procedure to remove a small portion of tissue for laboratory examination, is the only way to determine whether you have mesothelioma. Depending on what area of your body is affected, your doctor selects the right biopsy procedure for you. Options include:
- Fine-needle aspiration. The doctor removes fluid or a piece of tissue with a small needle inserted into your chest or abdomen.
- Thoracoscopy. Thoracoscopy allows the surgeon to see inside your chest. In this procedure, the surgeon makes one or more small incisions between your ribs. A tube with a tiny video camera is then inserted into your chest cavity — a procedure sometimes called video-assisted thoracoscopic surgery (VATS). Special surgical tools allow your surgeon to cut away tissue for testing.
- Laparoscopy. Laparoscopy allows the surgeon to see inside your abdomen. Using one or more small incisions into your abdomen, the surgeon inserts a tiny camera and special surgical tools to obtain a small piece of tissue for examination.
- Thoracotomy. Thoracotomy is surgery to open your chest between the ribs to allow a surgeon to check for signs of disease. He or she removes a sample of tissue for testing.
- Laparotomy. Laparotomy is surgery to open your abdomen to allow a surgeon to check for signs of disease. He or she removes a sample of tissue for testing.
The tissue sample is analyzed under a microscope to see whether the abnormal tissue is mesothelioma and what types of cells are involved. The type of mesothelioma you have determines your treatment plan.
Once mesothelioma is diagnosed, your doctor orders other tests to determine the extent, or stage, of the cancer. Imaging tests that may help determine the stage of your cancer include:
- Chest X-ray
- CT scans of the chest and abdomen
- Magnetic resonance imaging (MRI)
- Positron emission tomography (PET)
Once the extent of pleural mesothelioma is determined, a stage is assigned. Formal stages aren’t available for other types of mesothelioma because these types are rare and aren’t well studied. The stages of pleural mesothelioma are:
- I. Stage I pleural mesothelioma is considered localized cancer, meaning it’s limited to one portion of the lining of the chest.
- II. Stage II mesothelioma may have spread beyond the lining of the chest to the diaphragm or to a lung.
- III. Stage III mesothelioma may have spread to other structures within the chest and may involve nearby lymph nodes.
- IV. Stage IV mesothelioma is an advanced cancer that has spread to distant areas (metastasized). Mesothelioma most commonly spreads (metastasizes) to the brain, lymph nodes in the chest and areas of the lung that are away from the tumor.
Treatments and drugs
What treatment you undergo for mesothelioma depends on your health and certain aspects of your cancer, such as its stage and location. Unfortunately, mesothelioma often is an aggressive disease and for most people a cure isn’t possible. Mesothelioma is usually diagnosed at an advanced stage — when it isn’t possible to remove the cancer through an operation. Instead, your doctor may work to control your cancer to make you more comfortable. Some people want to do everything they can to treat their cancer, even if that means enduring side effects for a small chance of an improvement. Others prefer treatments that make them comfortable so that they can live their remaining months as symptom-free as possible.
Surgeons work to remove mesothelioma in instances where it is diagnosed at an early stage. Sometimes it isn’t possible to remove all of the cancer. In those cases, surgery may help to reduce the signs and symptoms caused by mesothelioma spreading in your body. Surgical options may include:
- Surgery to decrease fluid buildup. Pleural mesothelioma may cause fluid to build up in your chest, causing difficulty breathing. Surgeons insert a tube or catheter into your chest to drain the fluid. Surgeons may also inject medicine into your chest to prevent fluid from returning (pleurodesis).
- Surgery to remove the tissue around the lung or abdomen. Surgeons may remove the tissue lining the ribs and the lungs (pleurectomy) or the tissue lining the abdominal cavity (peritonectomy) in order to relieve signs and symptoms of mesothelioma.
- Surgery to remove as much of the cancer as possible (debulking). If all of the cancer can’t be removed, surgeons may attempt to remove as much as possible.
- Surgery to remove a lung and the surrounding tissue. Removing the affected lung and the tissue that surrounds it may relieve signs and symptoms of pleural mesothelioma. This procedure also allows doctors to use higher doses of radiation against any remaining mesothelioma, since they won’t need to worry about protecting your lung from damaging radiation.
Chemotherapy uses chemicals to kill cancer cells. Systemic chemotherapy travels throughout the body and may shrink or slow the growth of a pleural mesothelioma that can’t be removed using surgery. Chemotherapy may also be used before surgery (neoadjuvant chemotherapy) to make an operation easier or after surgery (adjuvant chemotherapy) to reduce the chance that cancer will return.
Chemotherapy drugs may also be heated and administered directly into the abdominal cavity (intraperitoneal chemotherapy), in the case of peritoneal mesothelioma, or into the chest cavity (intrapleural chemotherapy), in the case of pleural mesothelioma. Using this strategy, chemotherapy drugs can reach the mesothelioma directly without injuring healthy cells in other parts of the body. This allows doctors to administer higher doses of chemotherapy drugs.
Intraperitoneal chemotherapy may also be used to reduce the signs and symptoms of peritoneal mesothelioma that can’t be removed through surgery.
Radiation therapy focuses high-energy beams to a specific spot or spots on your body. Radiation may reduce signs and symptoms in people with pleural mesothelioma. Doctors aim radiation at the entire chest to obtain the best result. However, many sensitive organs are in the chest, such as the heart, lungs, esophagus and spinal cord, so doctors must use low doses of radiation to spare these organs. Radiation therapy is sometimes used after biopsy or surgery to prevent mesothelioma from spreading to the surgical incision.
Radiation therapy is used occasionally in people with peritoneal mesothelioma to reduce signs and symptoms caused by the cancer.
Surgery, chemotherapy and radiation therapy may be combined. This aggressive therapy can be grueling and may not be appropriate for everyone. Younger, healthier people and those with earlier stage mesothelioma may be more able to endure this treatment. Combination therapy has shown the most promise in treating mesothelioma. However, most people will eventually experience a recurrence of this cancer despite aggressive treatment. Combination therapy has been used in both pleural mesothelioma and peritoneal mesothelioma.
People with mesothelioma may opt for a clinical trial for a chance to try new types of treatment. However, a cure isn’t guaranteed. Carefully consider your treatment options and talk to your doctor about what clinical trials are open to you. Your participation in a clinical trial may help doctors better understand how to treat mesothelioma in the future. Clinical trials are currently investigating a number of targeted drugs. Targeted drug therapy uses drugs to attack specific abnormalities within cancer cells. Targets being studied in mesothelioma include a substance that cancer cells make to attract new blood vessels to bring the cancer oxygen and nutrients. Another target is an enzyme that helps cancer cells develop resistance to chemotherapy drugs. Researchers hope drugs that target these areas can help kill mesothelioma cells.
Pericardial mesothelioma and mesothelioma of the tunica vaginalis are very rare and can be very aggressive. Early-stage cancer may be removed through surgery. Doctors have yet to determine the best way to treat later stage cancers, though. Your doctor may recommend other treatments to improve your quality of life. Mesothelioma can cause pressure within your chest that can make you feel as though you’re always short of breath. Breathlessness can be distressing. Your doctor may recommend using an oxygen mask or taking medications to make you more comfortable, but often these aren’t enough. Combining your doctor’s recommended treatments with complementary and alternative approaches may help you feel better.
Alternative treatments that have shown some promise in helping people cope with breathlessness include:
- Acupuncture. Acupuncture uses thin needles inserted at precise points into your skin.
- Breath training. A nurse or physical therapist can teach you breathing techniques to use when you feel breathless. Sometimes you may feel breathless and begin to panic. Implementing these techniques may help you feel more in control of your breathing.
- Relaxation exercises. Slowly tensing and relaxing different muscle groups may help you feel more at ease and breathe easier. Your doctor may refer you to a therapist who can teach you relaxation exercises so that you can do them on your own.
- Sitting near a fan. Directing a fan to your face may help ease the sensation of breathlessness.
Most people with mesothelioma were exposed to the asbestos fibers at work. Workers who may encounter asbestos fibers include:
- Factory workers
- Insulation manufacturers
- Railroad workers
- Ship builders
- Gas mask manufacturers
- Construction workers
- Auto mechanics
Ask your employer whether you have a risk of asbestos exposure on the job. Follow all safety precautions in your workplace, such as wearing protective equipment. You may also be required to shower and change out of your work clothes before taking a lunch break or going home. Talk to your doctor about other precautions you can take to protect yourself from asbestos exposure. Older homes and buildings may contain asbestos. In many cases, it’s more dangerous to remove the asbestos than it is to leave it intact. Breaking up asbestos may cause fibers to become airborne, where they can be inhaled. Consult experts trained to detect asbestos in your home. These experts may test the air in your home to determine whether the asbestos is a risk to your health. Don’t attempt to remove asbestos from your home — hire a qualified expert. The Environmental Protection Agency offers advice on its Web site for dealing with asbestos in the home.