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What is mesothelioma?

On this page, we explain what mesothelioma is, the different types of mesothelioma and who is most at risk of developing mesothelioma.

On this page:

What is mesothelioma?

Mesothelioma is a type of cancer that begins to grow in the lining of certain organs. Most commonly it affects the lining of the lungs (called the pleura). But it can also affect the lining of the abdomen or the lining of the heart. This information focuses on mesothelioma of the chest, sometimes called malignant pleural mesothelioma.

Inside your chest are two thin layers of cells – called the pleura or pleural membranes.  Each layer is about as thin as the skin of a balloon. The inner layer covers your lungs and the outer layer lines the inside of your rib cage. 

The space between the two layers is called the pleural space and it normally contains a small amount of fluid. This fluid lubricates the two surfaces and lets your lungs and chest wall move and expand as you breathe in and out. 

Meso diagram 2

Usually mesothelioma affects only one side of your chest. As the cancer cells grow and multiply, they form lots of small clumps, called tumours. These tumours are scattered throughout the lining of your lung and rib cage causing it to become thicker. 

What are the different types of mesothelioma?

There are three different types of mesothelioma of the chest:

  • Epithelioid mesothelioma is the most common type and accounts for around 75% of cases. This type of mesothelioma grows more slowly than others.
  • Sarcomatoid mesothelioma is less common. It tends to progress more quickly and has a poorer outcome from treatment.
  • Biphasic mesothelioma is also uncommon. Biphasic tumours have some parts which are epithelioid and some parts which are sarcomatoid.

Who’s at risk of mesothelioma?

The main cause of mesothelioma is breathing in asbestos dust. Asbestos is a naturally occurring fibre that was widely used in construction and other industries until the late 1990s. It was used to insulate and fireproof buildings and was commonly used in ceiling tiles, pipe insulation, boilers and spray coatings used on ceilings and walls.

Asbestos fibres are extremely small. When you breathe them in, they get lodged inside your lungs. These fibres cause persistent irritation to the lungs, which in some people can lead to mesothelioma. It’s not known why some people with asbestos in their lungs develop mesothelioma and others don’t. 
The use of products containing asbestos was banned in the UK in 1999. But it is still found today in many buildings, including homes, public buildings and hospitals. There are now strict guidelines about removing asbestos safely.

Mesothelioma takes a long time to develop. It’s normal for people to get the first symptoms 30 to 40 years after they were first exposed to asbestos. So people who have symptoms now might have been exposed many years ago. 

People who worked in industries which used asbestos are at higher risk of developing mesothelioma. This includes ship-building, construction and insulation work, but asbestos exposure could have occurred in other jobs.

You can also develop mesothelioma if you lived with someone who worked with asbestos. They may have carried asbestos fibres home on their clothing, where family members could breathe them in. Some people who develop mesothelioma can’t remember coming into contact with asbestos and might not have been aware they were exposed to it.

Older people have a higher risk of mesothelioma than younger people. This is because they’re more likely to have come into contact with asbestos before the dangers were known. It’s also because it takes many years for mesothelioma to develop. 

Next: Symptoms of mesothelioma

Download our mesothelioma information (PDF, 166KB)

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