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TNM staging

The breast cancer TNM staging system is the most common way that doctors stage breast cancer. TNM stands for:

  • tumour
  • node
  • metastasis

Your scans and tests give some information about the stage of your cancer. But your doctor might not be able to tell you the exact stage until you have surgery.

Doctors may also use a number staging system.

Other tests on the breast cancer cells

Your doctor also uses other information about your breast cancer. This information helps to work out your overall stage, your outlook (prognosis) and treatment plan. These includes:

  • receptors for the female hormones (oestrogen and progesterone)
  • HER2 status (human epidermal growth factor receptor 2)
  • the grade of the cancer

By using a tissue sample of your cancer, doctors can find out if you are oestrogen or progesterone positive, or negative. This depends on the amount of these receptors seen in the sample. 

They also look at the levels of the protein HER2. Some breast cancers have large amounts of human epidermal growth factor receptor 2 (HER2). They are called HER2 positive cancers. HER2 makes the cancer cells grow and divide. Breast cancers that are HER2 positive generally grow more quickly.

The grade describes how a cancer cell looks under the microscope and whether they are similar or very different to normal cells.

Please remember staging for breast cancer is very complex. Many different factors are considered before doctors can confirm your final stage. Do speak to your breast doctor or nurse if you have any questions about your stage.
 

The TNM system

Here is a slightly simplified description of the TNM staging system for breast cancer.

Tumour (T)

Tumour describes the size of the tumour (area of cancer). This is a simplified description of the T stage.

TX means that the tumour size can't be assessed.

Tis (DCIS). DCIS means ductal carcinoma in situ. It is a pre invasive breast cancer. The cancer cells are in breast ducts and have not started to spread into the surrounding breast tissue.

Tis (Paget) Paget's disease is a rare skin condition of the nipple that is associated with some breast cancersAn early symptom of this can be a rash on the nipple. Sometimes there may be invasive breast cancer with Paget’s. In this situation it is staged by the size of the cancer. 

T1 means that the tumour is 2 centimetres (cm) across or less.

Diagram showing a stage T1 breast cancer

T1 is further divided into 4 groups:

  • T1mi means the tumour is 0.1cm across or less
  • T1a means the tumour is more than 0.1 cm but not more than 0.5 cm
  • T1b means the tumour is more than 0.5 cm but not more than 1 cm
  • T1c means the tumour is more than 1 cm but not more than 2 cm

T2 means that the tumour is more than 2 centimetres but no more than 5 centimetres across.

Diagram showing a stage T2 breast cancer

T3 means the tumour is bigger than 5 centimetres across.

Diagram showing stage T3 breast cancer

T4 is divided into 4 groups:

  • T4a means the tumour has spread into the chest wall (the structures surrounding and protecting the lungs)
  • T4b means the tumour has spread into the skin and the breast might be swollen
  • T4c means the tumour has spread to both the skin and the chest wall
  • T4d means inflammatory carcinoma – this is a cancer in which the overlying skin is red, swollen and painful
Diagram showing the position of the chest wall which is behind the breast and includes the muscle and ribs. If breast cancer spreads to these areas it is called stage T4 in the TNM staging system

Doctors may also use a number staging system.

Node (N)

Node (N) describes whether the cancer has spread to the lymph nodes.

Your doctor might use:

  • pathological staging if you have surgery
  • clinical staging if you don't have surgery

Pathological staging. Doctors stage you by using the tissue the surgeon removes during an operation. This is also called surgical staging. You might see your pathological stage written as pTNM.

Clinical staging means the doctor stages you after examining you and looking at test and scan results. Doctors use clinical staging if you don’t have surgery straight away. You might see your clinical stage written as cTNM.

Pathological node staging

Below is a simplified description using the pathological staging for nodes in breast cancer.

pNX means that the lymph nodes can't be assessed (for example, if they were previously removed).

pN0 means there are no cancer cells in any nearby nodes or only isolated tumour cells (ITCs).

Isolated tumour cells (ITCs) are small clusters of cancer cells less than 0.2 mm across, or a single tumour cell, or a cluster of fewer than 200 cells in one area of a lymph node. Lymph nodes containing only isolated tumour cells are not counted as positive lymph nodes.

pN1

pN1 is divided into 4 groups

pN1mi means one or more lymph nodes contain areas of cancer cells called micrometastases that are larger than 0.2mm. Or the nodes contain more than 200 cancer cells but are less than 2mm.

pN1a means that cancer cells have spread (metastasised) into 1 to 3 lymph nodes and at least one is larger than 2mm.

pN1b means there are cancer cells in the lymph nodes behind the breastbone (the internal mammary nodes) found with a sentinel node biopsy.

pN1c means there are cancer cells in 1 to 3 lymph nodes in the armpit and in the lymph nodes behind the breastbone.

pN2

N2 is divided into 2 groups:

pN2a means there are cancer cells in 4 to 9 the lymph nodes in the armpit, and at least one is larger than 2 mm.

pN2b means there are cancer cells in the lymph nodes behind the breast bone (the internal mammary nodes), which have been seen on a scan or felt by the doctor. There is no evidence of cancer in lymph nodes in the armpit.

pN3

pN3 is divided into 3 groups:

pN3a means there are cancer cells in 10 or more lymph nodes in the armpit and at least one is larger than 2mm, or there are cancer cells in the nodes below the collarbone.

pN3b means there are cancer cells in lymph nodes in the armpit and lymph nodes behind the breastbone.

pN3c means there are cancer cells in lymph nodes above the collarbone.

Diagram showing N3C lymph nodes above the collarbone

Clinical node staging

Clinical staging means the doctor stages you after examining you and looking at test and scan results. Doctors use clinical staging if you don’t have surgery straight away. You might see your clinical stage written as cTNM.

This is a simplified description using the clinical staging for nodes in breast cancer.

cNX means it is not possible to assess the lymph nodes (for example, if they were previously removed).

cN0 means there are no signs of cancer in the lymph nodes following scans and examination. 

cN1 

cN1 is divided into 2 groups

cN1 means the cancer cells have spread to one or more lymph nodes in the lower and middle part of the armpit. The lymph nodes move a little when they are felt and are not stuck to surrounding tissue.

cN1mi means the cancer cells in the lymph nodes are very small and can only be seen under a microscope. These are called micrometastases. They are larger than 0.2mm, but no larger than 2mm.

cN2 

cN2 is divided into 2 groups 

cN2a means the cancer cells in the armpit are stuck together or fixed to other areas of the breast such as the muscle.

cN2b means there are cancer cells in the lymph nodes behind the breast bone (the internal mammary nodes). There is no sign of cancer in the lymph nodes in the armpit.

cN3

cN3 is divided into 3 groups 

cN3a means cancer cells are seen in one or more lymph nodes below the collar bone. 

cN3b means cancer cells are seen in one or more lymph nodes around the armpit and breast bone. 

cN3c means cancer cells are seen in one more lymph nodes above the collar bone. 

Metastasis (M)

Metastasis (M) describes whether the cancer has spread to a different part of the body.

M0 means that there is no sign that the cancer has spread.

cMo(i+) means there is no sign of the cancer on physical examination, scans or x-rays. But cancer cells are present in blood, bone marrow, or lymph nodes far away from the breast cancer – the cells are found by laboratory tests.

cM1 means the cancer has spread to another part of the body, seen on scans or felt by the doctor.

pM1 means that cancer measuring more than 0.2 mm across has spread to another part of the body. This has been confirmed by examining tissue from a biopsy, or surgery and scans.
 

Diagram showing M stages breast

Treatment

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

The stage of the cancer and these other factors can also give an idea of your outlook (prognosis).

Other factors that may influence treatment are:

  • the grade of your cancer cells
  • whether you have had your menopause
  • whether your cancer cells have receptors for particular cancer drugs

Your doctor will take many different factors into account when deciding which treatment is best for you.

Treatment may include:

  • surgery
  • radiotherapy
  • chemotherapy
  • hormone therapy
  • targeted cancer drug therapy

 Bisphosphonates 

You may also have treatment with a group of drugs called bisphosphonates. You may have this if you have early breast cancer and no longer have periods (post menopausal). They can help reduce the risk of the cancer spreading to the bones.

People with advanced breast cancer may have this to treat symptoms such as bone pain. 

Your doctor will let you know if this is suitable for you, 

Last reviewed: 
21 Jul 2020
Next review due: 
21 Jul 2023
  • AJCC Cancer Staging Manual (8th edition)
    American Joint Committee on Cancer
    Springer, 2017

  • TNM Classification of Malignant Tumours (8th edition)
    Union for International Cancer Control
    J Brierley, M Gospodarowicz and C Wittekind   
    Wiley Blackwell, 2017

  • Early Breast Cancer: ESMO Clinical Practice Guidelines 2019
    F Cardoso and others
    Annals of Oncology, 2019. Volume 30, Issue 8, Pages 1194–1220

  • Early and locally advanced breast cancer: diagnosis and treatment
    National Institute for Health and Care Excellence (NICE) June 2018

  • Advanced breast cancer: diagnosis and treatment
    National Institute for Health and Care Excellence (NICE), 2009 (updated August 2017)

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