Coronavirus and cancer

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The stage of a cancer tells the doctor where it is, how big it is and whether it has spread. The tests and scans you have when diagnosing your cancer give some information about the stage. Knowing the stage helps your doctor decide about the treatment you need.

Most people who are diagnosed with mesothelioma have an advanced stage of cancer.

The staging used for mesothelioma in the chest (pleural mesothelioma) is different to the staging for mesothelioma in the abdomen (peritoneal mesothelioma).

IMIG stages

The staging system most commonly used in the UK for pleural mesothelioma is called the International Mesothelioma Interest Group (IMIG) system. 

It is based on the TNM (tumour, node, metastasis) system, which is used for many different cancers. This describes:

  • the size and position of the primary mesothelioma tumour (T)
  • whether mesothelioma cells have spread to nearby lymph nodes (N)
  • whether mesothelioma cells have spread to other parts of the body - metastases (M)

Once the TNM categories have been decided, this information is grouped together to give the stage. Stage 1 is the earliest stage and stage 4 is the most advanced stage.

Stage 1

Mesothelioma cells are in the pleura around the lung on one side of your chest.

Stage 1a 

Mesothelioma cells are in the outer layer of the pleura (parietal pleura) on one side of the chest.

Stage 1b

Mesothelioma cells are in the inner layer of the pleura (visceral pleura), but only on one side of the chest. They have not spread to your lung tissue or diaphragm.

Stage 2

Mesothelioma has spread to both layers of the pleura on one side of the body, and has enlarged to form a tumour mass on the pleural tissue around the lungs, or has started to spread into the diaphragm muscle or the lung tissue.

Stage 3

Mesothelioma has spread to the chest wall or the covering of the heart (pericardium), but is still potentially removable by surgery. Or it has spread to the lymph nodes on the same side of the chest.

Stage 4

Mesothelioma cannot be removed by surgery because it has spread to different parts of the chest wall, or has grown through the diaphragm into the peritoneum, or to the pleura on the other side of the body, or to the chest organs, or through to the inner layer of the pericardium. 

Or it has spread to the lymph nodes on the other side of the chest, or above the collarbone. Or has spread to other parts of the body.

Peritoneal mesothelioma stages

There is no established staging system for peritoneal mesothelioma. Sometimes the doctors may use the TNM system used for pleural mesothelioma.


The stage of your cancer helps your doctor to decide which treatment you need. Treatment also depends on:

  • your type of cancer (the type of cells the cancer started in)
  • where the cancer is 
  • other health conditions that you have
Last reviewed: 
04 Sep 2018
  • AJCC Cancer Staging Manual (7th edition)
    American Joint Committee on Cancer
    Springer, 2010

  • Biology and management of malignant pleural mesothelioma. 

    P Zucali and others

    European Journal of Cancer, (2006). 42(16), 2706-2714

  • Cancer and its management, 7th edition
    J Tobias and D Hochhauser
    Wiley Blackwell, 2015

Information and help