What is mesothelioma?

This information explains what mesothelioma is and who might be at risk.

Mesothelioma is a type of cancer that begins to grow in the pleural membrane. Your chest contains two thin layers of cells – an outer layer that lines the inside of your rib cage and an inner layer that covers your lungs. These layers are called the pleura or pleural membrane. Each layer is about as thin as the skin of a balloon.

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

Mesothelioma can affect a similar lining around your abdomen or heart, but this is less common. This information focuses on mesothelioma of the chest, sometimes called malignant pleural mesothelioma.

Usually mesothelioma affects only one side of your chest. As the cancer cells grow and multiply, they form clumps called tumours. Sometimes there’s just one large tumour. More commonly, there are lots of small tumours scattered throughout your pleural membrane. These cause the pleural membrane to become thicker.

There are three different types of mesothelioma:

  • Epithelioid mesothelioma is the most common type. This type of mesothelioma grows more slowly than others, so it might respond better to treatments.
  • Sarcomatoid mesothelioma is less common. It tends to progress more quickly and has a poorer outcome from treatment.
  • Biphasic mesothelioma is also uncommon. It’s more aggressive than epithelioid mesothelioma but grows more slowly than sarcomatoid mesothelioma.

Who is at risk?

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.

The use of products containing asbestos was banned in the UK in 1999. But it’s still found today in many buildings, including homes, schools 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. They include:

  • carpenters and joiners
  • plumbers, heating and ventilation engineers
  • electricians, electrical fitters
  • pipe fitters
  • metal plate workers, shipwrights, riveters
  • labourers in other construction trades
  • sheet metal workers
  • construction operatives
  • energy plant operatives
  • painters and decorators
  • building inspectors
  • vehicle body builders and repairers
  • metalworking production and maintenance fitters
  • shipbuilding workers
  • railway engineering workers
  • people who have worked on DIY projects, particularly Artexing ceilings or working with guttering or insulation materials

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 partly because it takes so many years for mesothelioma to develop, but also because they are more likely to have come into contact with asbestos before the dangers were known.

Mesothelioma is much less common in women, probably because they are less likely to have worked directly with asbestos.

Next: Symptoms of mesothelioma >

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Last medically reviewed: November 2017. Due for review: November 2020

This information uses the best available medical evidence and was produced with the support of people living with lung conditions. Find out how we produce our information. If you’d like to see our references get in touch.