About mesothelioma types

In the UK, more than 2,700 people are diagnosed with mesothelioma (pronounced mee-so-thee-lee-oma) each year.

Mesothelioma is a cancer of the mesothelium. The mesothelium is a thin lining (membrane) that covers the outer surface of many organs in the body. It also lines the spaces (cavities) within the body, such as the chest and abdominal cavity.

The mesothelium has different names depending on where it is in the body. For example:

the mesothelium in the chest is called the pleura
the mesothelium in the tummy (abdomen) is called the peritoneum.

The mesothelium is made up of mesothelial cells. If these cells develop abnormally, they can develop into cancer called malignant mesothelioma. Malignant mesothelioma is usually just called mesothelioma.

When mesothelioma affects the chest, it is called pleural mesothelioma. When it affects the abdomen, it is called peritoneal mesothelioma. Pleural mesothelioma is much more common.

Pleural mesothelioma

The lungs sit in the chest, on either side of the heart. When you breathe air into your lungs, they supply oxygen to your body.

The lungs are covered by a lining (membrane) called the pleura. The pleura is made up of 2 layers:

the inner layer covers the lungs
the outer layer lines the ribcage and a sheet of muscle called the diaphragm – the diaphragm separates the chest from the tummy.

The space between the 2 layers is called the pleural cavity. The pleural cavity has a small amount of fluid in it. This fluid acts as a lubricant. This allows the lungs to move in and out smoothly so you can breathe easily.

Pleural mesothelioma starts as small lumps (nodules) that grow and spread throughout the pleura. As these lumps grow together, the pleura becomes thicker. This means the lungs cannot move as easily and you become breathless. Fluid may also collect between the 2 layers of the pleura. This is called a pleural effusion.

Structure of the lungs and pleura

A diagram of the lungs and pleura, showing a close-up of the inner pleura, outer pleura and the pleural cavity. — Image: The illustration shows the lungs in the chest. It shows the windpipe (trachea) coming down from the neck into the chest. About halfway down the chest, the windpipe divides into two tubes. One tube goes into the left lung. The other tube goes into the right lung. There are ribs around the outer side of each lung. Underneath the lungs, and going across the width of the body, is a muscle called the diaphragm. Surrounding each lung is a thin lining (membrane), which has two layers. This is called the pleura. The layer closest to each lung is called the inner pleura. The layer which lines the chest wall is called the outer pleura. There is a small space between the two layers of the pleura. This space is called the pleural cavity. There are groups of pea-sized lymph nodes in the chest. They are connected to each other by fine tubes. The lymph nodes are close to the windpipe. There are also lymph nodes on each side of the neck and in the shoulder area.

Peritoneal mesothelioma

The organs in the tummy (abdomen) are covered by a lining (membrane) called the peritoneum. It has an inner and outer layer. The inner layer covers the organs in the abdomen. This is called the visceral peritoneum. The outer layer lines the abdominal wall. This is called the parietal peritoneum.

The peritoneum helps protect the organs in the abdomen and keeps them in place.

Mesothelioma can cause the layers of the peritoneum to thicken. Mesothelioma can also cause fluid to build up between the 2 layers. This is called ascites.

Side view of the tummy (abdomen) showing the peritoneum

A diagram of the side view of the tummy, showing the internal organs including the liver, stomach and bowel. Also shown is the peritoneum, the inner and outer layers, and the space between them called the peritoneal cavity. — Image: The illustration shows a side view of the tummy, which is also called the abdomen. The person is facing to the left. It shows the internal organs in the tummy, including the liver, the stomach and the bowel. These are surrounded by the peritoneum, which is a thin membrane. The peritoneum has two layers. The outer layer lines the wall of the tummy, and the inner layer covers the internal organs. There is a small space between these layers, called the peritoneal cavity.

Cell types of mesothelioma

Pleural and peritoneal mesothelioma can be grouped by how the cells look under a microscope. The different types include:

epithelioid – this is the most common type
sarcomatoid
mixed or biphasic – this has both epithelioid and sarcomatoid cells
multi-cystic and well-differentiated papillary mesothelioma – these are rare and slow growing types of peritoneal mesothelioma.

Knowing the type of cell that is affected may give your doctors more information about:

the best treatment for you
how the mesothelioma may respond to treatment.

Rare types of mesothelioma

Very rarely, mesothelioma may develop in the outer lining of other organs. This includes the:

heart (pericardial mesothelioma)
testes (testicular mesothelioma).

Macmillan is also here to support you. If you would like to talk, you can:

call the Macmillan Support Line for free on 0808 808 00 00.
chat to our specialists online.
visit our mesothelioma forum to talk with people who have been affected by mesothelioma, share your experience, and ask an expert your questions.

References

Below is a sample of the sources used in our mesothelioma cancer information. If you would like more information about the sources we use, please contact us at informationproductionteam@macmillan.org.uk

Kusamura S, Kepenekian V, Villeneuve L, Lurvink RJ, Govaerts K, De Hingh IHJT, Moran BJ, Van der Speeten K, Deraco M, Glehen O; PSOGI. Peritoneal mesothelioma: PSOGI/EURACAN clinical practice guidelines for diagnosis, treatment and follow-up. Eur J Surg Oncol. 2021 Vol, 47(1) pp6-59. [accessed April 2024].

Popat, S., Baas P., Faivre-Finn, C., Girard, N., Nicholson, A., Nowak, A., Opitz, I., Scherpereel, A, and Reck, M. 2021. ESMO Pleural mesothelioma guidelines. Malignant pleural mesothelioma: ESMO Clinical Practice Guidelines for diagnosis, treatment and follow-up. Available from: https://www.annalsofoncology.org/action/showPdf [accessed April 2024].

Cancer Information Development team

Author

Dr David Gilligan

Reviewer

Consultant Clinical Oncologist

Addenbrookes Hospital, Cambridge

Date reviewed

Reviewed: 01 February 2025

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Next review: 01 February 2028

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