Mesothelioma stages

Staging for mesothelioma refers to the size of the cancer and whether it has spread.
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Understanding mesothelioma staging

The stage of mesothelioma refers to its size and the thickness of the pleura. The stage also tells you if the cancer has spread to the lymph nodes, and beyond the area of the body where it first started. Knowing the stage of the cancer helps you and your doctors decide on the best treatment for you.

There are different staging systems. Many are based on the TNM system:

  • T describes the size of the cancer.
  • N describes whether the cancer has spread to the lymph nodes and which nodes are involved. For example, N0 means that no lymph nodes are affected, while N1 means there are cancer cells in the lymph nodes.
  • M describes whether the cancer has spread (metastasised) to another part of the body. For example, M0 means the cancer has not spread to other parts of the body, while M1 means the cancer has spread to other parts of the body.

We understand that waiting to know the stage and grade of your cancer can be a worrying time. We're here if you need someone to talk to. You can:

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Staging of pleural mesothelioma

The staging system that is often used for pleural mesothelioma is written by the International Association for the Study of Lung Cancer (IASLC). It is based on the TNM system. 

Stage 1

The cancer is limited to the pleura, in one side of the chest. It is 12mm or less in thickness. The cancer has not spread to the lymph nodes.

Stage 2

The cancer is the same as stage 1 but has also spread to nearby lymph nodes (N1).

Or the cancer is 12mm thick or less and has grown into the tissue beneath the pleura. The cancer has not spread to the lymph nodes.

Or the cancer is more than 12mm thick but less than 30mm and may or may not have spread into the tissue beneath the pleura. It has not spread to the lymph nodes.

Stage 3

Stage 3 pleural mesothelioma is divided into Stage 3a and Stage 3b.

Stage 3a

  • The cancer is up to 12mm thick and has spread to lymph nodes on the other side of the chest (N2).
  • Or the cancer is between 12mm and 30mm thick and may also have spread into the tissue beneath the pleura. It has also spread to lymph nodes nearby (N1) or further away (N2).
  • Or the cancer is 30mm or more and involving tissue beneath the pleura. It may or may not have spread to lymph nodes nearby (N1) or further away (N2).

Stage 3b

The cancer is any thickness and has spread further into the chest wall.

  • It may have affected, for example, the ribs, oesophagus or windpipe (trachea).
  • It may also have spread through the lining of the heart, or through the diaphragm.
  • It may or may not have spread to nearby lymph nodes, or lymph nodes further away on the other lung.

Stage 4

The cancer has spread outside of the chest to another area of the body (metastasis or M1).

 

MACD236 Structure of the lungs and pleura
Image: A diagram of the lungs and pleura, showing a close-up of the inner pleura, outer pleura and the pleural cavity. Long description: 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.

 

Staging of peritoneal mesothelioma

There is no specific staging system for peritoneal mesothelioma. But your cancer team may sometimes use the Peritoneal Cancer Index (PCI) system.

This looks at:

  • the number of tumours in the peritoneum
  • the size of the tumours
  • where the tumours are in the tummy area (abdomen)
  • whether the cancer has spread outside the peritoneum or to any lymph nodes.

PCI is only used in specialist centres. You can ask your cancer doctors for more information if you have any questions.

About our information

This information has been written, revised and edited by Macmillan Cancer Support’s Cancer Information Development team. It has been reviewed by expert medical and health professionals and people living with cancer.

  • 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 SME

Dr David Gilligan

Reviewer

Consultant Clinical Oncologist

Addenbrookes Hospital, Cambridge

Date reviewed

Reviewed: 01 February 2025
|
Next review: 01 February 2028
Trusted Information Creator - Patient Information Forum
Trusted Information Creator - Patient Information Forum

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