Mesothelioma

Friday 30 September, 2011

Reviewed: Dr Malcolm Feigen, Senior Radiation Oncologist, Austin Health; Dr Paul Jenkinson, GP; Mary Duffy, Lung Nurse Specialist, Peter MacCallum; Prof Bill Musk, Respiratory Physician; Kathryn Turner, Social Worker, Slater & Gordon Lawyers ; Jane McDermott, Principal, Maurice Blackburn Lawyers; Asbestos Diseases Society of Victoria

On this page: Mesothelioma in the chest | Mesothelioma in the abdomen | Causes of mesothelioma | Why is asbestos dangerous? | How common is mesothelioma? | Symptoms

Mesothelioma is a type of cancer affecting the mesothelial cells. These cells cover most organs inside the body. They form a coating known as the mesothelium.

The mesothelium makes a lubricating fluid that helps protect the organs as well as allowing them to move around. For example, this fluid makes it easier for the lungs to move inside the chest when you breathe.

The mesothelium is called the pleura in the chest area. Mesothelioma in the chest is called pleural mesothelioma. This is the most common type of mesothelioma.

The mesothelium is called the peritoneum in the abdomen. This mesothelioma is called peritoneal mesothelioma. This is a less common type of mesothelioma.

Occasionally, mesothelioma starts in the membrane around the heart or the reproductive organs. It forms growths shaped like small pieces of cauliflower. They grow and spread gradually to surrounding areas. A person may develop mesothelioma in more than one place but this is rare.

Tumours developing in the mesothelium can be non-cancerous (benign) or cancerous (malignant). Benign tumours can usually be taken out with surgery and there are no further problems. This site only discusses malignant mesothelioma and mainly those in the chest and abdomen.

Mesothelioma can also be divided into another three types according to how the cells look under a microscope:

  1. epithelioid: around 60 out of every 100 cases of mesothelioma are this type; people with this type generally have a better prognosis (outcome) than those with other types
  2. sarcomatoid (fibrous): these make up about 15 out of every 100 cases
  3. Mesothelioma mixed (biphasic): this means the mesothelioma is made up of both epithelioid and sarcomatoid cells. These make up about 25 out of every 100 cases.

Mesothelioma in the chest (pleural mesothelioma)

Pleural mesothelioma starts in the pleura. The pleura is the two layers of thin membrane that surround the lungs and line the chest wall. The inner layer is attached to the lungs and the outer layer lines the chest wall and diaphragm. Between the two layers is the pleural cavity. This cavity is almost empty. The two layers of pleura slide against each other. They're moist so that lungs can move smoothly against the chest wall as you breathe.

A diagram of the lungs

Sometimes mesothelioma can spread into the area around the heart (pericardium).

Mesothelioma in the abdomen (peritoneal mesothelioma)

Peritoneal mesothelioma starts in the peritoneum. This is the sheet of tissue covering and lining the internal organs in the abdomen. This sheet helps to protect the organs and allows them to move around within the abdomen. The peritoneum makes a fluid that helps to keep the abdominal organs moving freely and smoothly as we move around.

Causes of mesothelioma

Asbestos exposure

Mesothelioma is very strongly linked with asbestos exposure. Almost everyone diagnosed with mesothelioma was exposed to asbestos.

Asbestos is a mineral rock made up of masses of tiny fibres. For many decades, asbestos was mined and widely used in building materials and for insulation, fireproofing and sound absorption. It was used to insulate buildings, ships, car parts, household appliances and power stations.

There are three types of asbestos - blue, brown and white. All are linked to mesothelioma although blue and brown are more commomly linked. The health hazards of asbestos have become clear in recent decades.

Asbestos has been banned in Australia since 2004 and it is now illegal here to store, mine, import, sell, install or reuse any products containing asbestos. Any asbestos products already in place are allowed. However, great care needs to be taken if anything known to contain asbestos is to be disturbed or pulled down. There are strict regulations associated with removal and disposal of asbestos for areas greater than 10m2. See our ‘Services and information' section.

Most people are at low risk of asbestos exposure and mesothelioma. People who've been exposed to asbestos in their jobs are at greater risk. Such jobs include:

  • mining or milling asbestos
  • manufacture and repair of goods using raw asbestos fibres, such as brake linings
  • use of products containing asbestos, like in building and construction,
  • heating, shipyards, power stations, boiler making, gas fittings and plumbing
  • alteration, repair or demolition of buildings or other structures containing asbestos.

It may take over 20 years after exposure for any disease caused by asbestos to become evident (it can take up to and over 50 years).

However, most workers exposed to asbestos won't develop an asbestos-related disease.

Why is asbestos dangerous?

When asbestos is disturbed, it forms a dust made up of tiny fibres. This can easily be breathed in and cause serious health problems, notably:

  • pleural plaque
  • asbestosis
  • diffuse pleural thickening
  • benign pleural effusion
  • lung cancer
  • mesothelioma.

When asbestos is disturbed it sends out fibres into the air that can be inhaled by anyone nearby. Workers in mining and construction, plumbers, carpenters and auto mechanics have been at risk of exposure to asbestos.

It can also affect family members of workers who brought home asbestos fibres on their clothing and shoes from their work site.

It is not clear how asbestos fibres get into the peritoneal cavity. It is unlikely that they come through the wall of the gut. However, they may come in through the diaphragm. When asbestos fibres are taken into the body, cells react in an abnormal way. This may result in inflammation and scarring causing pleural plaque or diffuse pleural thickening. Or it may alter the DNA of the cells and result in the cells becoming malignant.

How common is mesothelioma?

Mesothelioma is a rare type of cancer but it is affecting more people. Australia has one of the highest rates of mesothelioma in the world. This is related to the high rate of asbestos use in mining, construction, manufacturing and home renovations over many years. In 2007 (the most recent data available), nearly 600 people were diagnosed with mesothelioma in Australia. Of these new cases, 81% were men.

In Victoria about 160 people are diagnosed each year. These figures are likely to change. Experts believe the number of people diagnosed with asbestos-related diseases will not peak until 2020. Since 1980 there have been about 13,000 new cases of mesothelioma in Australia.

Symptoms

In its early stages mesothelioma (pleural and peritoneal) may not cause many symptoms. It is only later, when the cancer moves into the underlying tissues or causes fluid to leak into the cavity in the chest or abdomen, that symptoms appear.

Symptoms of pleural mesothelioma

The cancer causes cells in the pleura to produce fluid, called a pleural effusion. The fluid builds up between the two layers of pleura and presses on the lungs. This can cause:

  • shortness of breath
  • a persistent dry cough
  • pain, which is often described as a heaviness or dull aching in the shoulder, arm, chest wall and upper abdomen. Some people describe it as like having pulled a muscle; others describe it as a sharp, stabbing or even ‘burning' pain
  • difficulty swallowing, a hoarse voice or coughing up sputum or blood - these are rare symptoms.

As the cancer progresses, it can grow into the lung, lymph nodes, chest wall, ribs, brain and liver, causing other symptoms.

Symptoms of peritoneal mesothelioma

Mesothelioma in the peritoneum (‘peritoneal mesothelioma') causes:

  • abdominal pain
  • swollen abdomen
  • poor appetite
  • nausea and vomiting
  • fever
  • bowel or urinary problems.

Symptoms of advanced stage disease

Advanced stage cancer usually means cancer that has spread from where it began to other parts of the body. You may hear doctors call this ‘metastatic', ‘progressive' or ‘secondary' cancer. Most people diagnosed with mesothelioma have advanced cancer, although at the time they are diagnosed they may not yet have symptoms of advanced cancer.

As well as the symptoms described above, other symptoms that may appear at this stage include:

  • severe weight loss
  • fatigue
  • fever
  • sweating
  • confusion due to chemical imbalances in the body or spread of the
  • cancer to the brain
  • lumps under the skin.

All symptoms discussed in this section can be caused by other, less serious diseases. However, if you or someone close to you has any of them (especially if you know you have been exposed to asbestos) you should see your doctor. If necessary they can do further tests to find the cause of your problems. 

If you've been exposed to asbestos in the past and develop shortness of breath, chest pain or other symptoms (pain, cough, weight loss), see your GP and ask for a referral for a chest x-ray or other tests they think may be necessary. Tell the doctor you've been exposed to asbestos. If any abnormalities show up on your x-ray or you remain unwell you should see a respiratory specialist.

Useful links

Asbestos Diseases Society of Victoria

Gippsland Asbestos Related Diseases Support Group Inc. (Gards)

Mesothelioma Causes (US website - some information may not apply in Australia)

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