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Mesothelioma; Causes, Symptoms, Prevention

 

Mesothelioma; Causes, Symptoms, Prevention

Malignant mesothelioma (me-zoe-thee-lee-O-muh) is a type of cancer that occurs in the thin layer of tissue that covers the majority of your internal organs (mesothelium).

Mesothelioma is an aggressive and deadly form of cancer. Mesothelioma treatments are available, but for many people with mesothelioma, a cure isn't possible.

Doctors divide mesothelioma into different types based on what part of the mesothelium is affected. Mesothelioma most often affects the tissue that surrounds the lungs (pleura). This type is called pleural mesothelioma. Other, rarer types of mesothelioma affect tissue in the abdomen (peritoneal mesothelioma), around the heart and around the testicles.

Mesothelioma is cancer of the mesothelium, a membrane that lines the inside of the body's cavities, such as the abdomen or chest. Three out of every four cases of mesothelioma disease begin in the chest cavity. Mesothelioma can also begin in the abdominal cavity and around the heart.

Regardless of where they originate, malignant cells from the mesothelium can invade and damage nearby tissues. Cancer cells can also metastasize, or spread, to other parts of the body.

Often by the time mesothelioma is diagnosed, the disease is advanced. The 5-year survival rate is around 5% to 10%. Most patients with mesothelioma of the lung die as a result of respiratory failure or pneumonia. Some patients get a small-bowel obstruction when the tumor extends through the diaphragm, a muscle that separates the chest and abdominal cavity. A smaller number people die of complications of the heart when the tumor invades the pericardium -- a thin sac that surrounds the heart -- and the heart itself.


Causes of Mesothelioma

In general, cancer begins when a series of changes (mutations) happens in a cell's DNA. The DNA contains the instructions that tell a cell what to do. The mutations tell the cell to grow and multiply out of control. The abnormal cells accumulate and form a tumor.

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.

The main risk factor for mesothelioma is working with asbestos. Asbestos is a group of minerals with thin microscopic fibers. Because these fibers are resistant to heat, fire, and chemicals and do not conduct electricity, asbestos has been mined and used widely in the construction, automotive, and other industries.

If tiny asbestos fibers are released into the air, as they are in the manufacturing process, they can be inhaled or swallowed, leading to serious health problems. As many as 75% of mesothelioma cases can be linked to exposure to asbestos at work. There is also 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. Cases of mesothelioma have also been seen in people living close to asbestos mines.

However, mesothelioma has been reported in some individuals without any known exposure to asbestos. Other, uncommon, but possible causes include:

Zeolites. These minerals are chemically related to asbestos. One of these related minerals, erionite, is common in the soil in some areas of Turkey, according to the American Cancer Society. Exposure to erionite is believed to be responsible for high rates of mesothelioma rates in those areas.

Radiation. The American Cancer Society notes that there have been a few published reports of mesotheliomas that developed following exposure to high doses of radiation to the chest or abdomen or after injections of thorium dioxide (Thorotrast), a material used by doctors in some chest X-rays until the 1950s.

SV40 virus. Some studies in laboratory animals have raised the possibility that infection with the simian virus 40 (SV40) might increase the risk of developing mesothelioma, according to the American Cancer Society. Some injectable polio vaccines given between 1955 and 1963 were contaminated with SV40, exposing as many as 30 million people in the U.S. to the virus. So far, the largest studies addressing this issue in humans have not found an increased risk for mesothelioma or other cancers among people who received the contaminated vaccines as children.

Genetics. Some experts believe certain people may be genetically predisposed to mesothelioma. Rates of the disease vary among populations.

Symptoms

Signs and symptoms of mesothelioma vary depending on where the cancer occurs.

Pleural mesothelioma, which affects the tissue that surrounds the lungs, causes signs and symptoms that may include:

  • Chest pain
  • Painful coughing
  • Shortness of breath
  • Unusual lumps of tissue under the skin on your chest
  • Unexplained weight loss

Peritoneal mesothelioma, which occurs in tissue in the abdomen, causes signs and symptoms that may include:

  • Abdominal pain
  • Abdominal swelling
  • Nausea
  • Unexplained weight loss
  • Other forms of mesothelioma

Signs and symptoms of other types of mesothelioma are unclear since these forms of the disease are very rare.

Pericardial mesothelioma, which affects the tissue that surrounds the heart, can cause signs and symptoms such as breathing difficulty and chest pains.

Mesothelioma of tunica vaginalis, which affects the tissue surrounding the testicles, may be first detected as swelling or a mass on a testicle.


When to see a doctor

See your doctor if you have signs and symptoms that worry you. Signs and symptoms of mesothelioma aren't specific to this disease and, due to the rarity of mesothelioma, are more likely to be related to other conditions. If any persistent signs and symptoms seem unusual or bothersome, ask your doctor to evaluate them. Tell your doctor if you've been exposed to asbestos.


Risk factors

Asbestos exposure: The primary risk factor for mesothelioma

Most mesotheliomas are thought to be related to asbestos exposure. Asbestos is a mineral that's found naturally in the environment. Asbestos fibers are strong and resistant to heat, making them useful in a wide variety of applications, such as in insulation, brakes, shingles, flooring, and many other products.

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 will settle in the lungs or in the stomach, where they can cause irritation that may lead to mesothelioma. Exactly how this happens isn't understood. It can take 20 to 60 years or more for mesothelioma to develop after asbestos exposure.

Most people with asbestos exposure never develop mesothelioma. This indicates that other factors may be involved in determining whether someone gets mesothelioma. 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. Exposure to these stray fibers over many years can put others in the home at risk of mesothelioma. People who work with high levels of asbestos can reduce the risk of bringing home asbestos fibers by showering and changing clothes before leaving work.

A family history of mesothelioma. If your parent, sibling or child has mesothelioma, you may have an increased risk of this disease.

Radiation therapy to the chest. If you had radiation therapy for cancer in your chest, you might have an increased risk of mesothelioma.

Complications

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
  • Pain caused by pressure on the nerves and spinal cord
  • Accumulation of fluid in the chest (pleural effusion), can compress the lung nearby and make breathing difficult

Prevention

Reducing your exposure to asbestos may lower your risk of mesothelioma.

Find out whether you work with asbestos

Most people with mesothelioma were exposed to asbestos fibers at work. Workers who may encounter asbestos fibers include:


  • Asbestos miners
  • Electricians
  • Plumbers
  • Pipefitters
  • Insulators
  • Shipyard workers
  • Demolition workers
  • Brake mechanics
  • Selected military personnel
  • Home remodelers

Ask your employer whether you have a risk of asbestos exposure on the job.

Follow your employer's safety regulations

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.


Be safe around asbestos in your home

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 asbestos is a risk to your health. Don't attempt to remove asbestos from your home — hire a qualified expert.

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