TNM staging for breast cancer
The stage of a cancer tells you how big it is and how far it has spread. It helps your doctor decide the best treatment for you. The TNM staging system stands for:
- tumour (cancer)
- node
- metastasis
The TNM staging system is the most common way to stage breast cancer in the UK. Doctors may also use a number staging system.
Staging for breast cancer is very complex. Many different factors are considered before doctors can confirm your final stage. The tests and scans you have give your doctor some information about the stage. But your doctor might not be able to tell you the exact stage until you have surgery.
Speak to your doctor or breast cancer nurse specialist if you have any questions about your staging.
Tumour (T)
Tumour describes the size or area of the cancer. This is a simplified description of the T stage.
TX means that the size of the cancer 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 cancers.
T1 means that the tumour is 2 centimetres (cm) across or less.
T1 is further divided into 4 groups:
- T1mi means the cancer is 0.1 cm across or less
- T1a means the cancer is more than 0.1 cm but not more than 0.5 cm
- T1b means the cancer is more than 0.5 cm but not more than 1 cm
- T1c means the cancer is more than 1 cm but not more than 2 cm
T2 means the cancer is more than 2 cm but no more than 5 cm.
T3 means the cancer is bigger than 5 cm.
T4 is divided into 4 groups:
- T4a means the cancer has spread into the chest wall
- T4b means the cancer has spread into the skin and the breast might be swollen
- T4c means the cancer has spread to both the skin and the chest wall
- T4d means inflammatory carcinoma. This is a rare type of breast cancer
Node (N)
Node (N) describes whether the cancer has spread to the 
. The diagram below shows the network of lymph nodes around the breast.
Your doctor might use the clinical staging or the pathological 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.
Pathological staging means the doctor stages your cancer by using the tissue removed during the operation. You might see your pathological stage written as pTNM.
We have included both clinical and pathological staging here. Talk to your doctor about which staging system they have used and why. They can help you understand more about your individual node stage.
Clinical node staging
There are several stages in the clinical node staging. This is a simplified description of the clinical node staging for 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 means the cancer cells have spread to one or more lymph nodes in the lower or 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. These are called micrometastases. They are larger than 0.2 mm, but no larger than 2 mm.
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 breastbone (the internal mammary nodes). There is no sign of cancer in the lymph nodes in the armpit.
cN3 is divided into 3 groups:
- cN3a means there are cancer cells in the lymph nodes below the collarbone.
- cN3b means there are cancer cells in the lymph nodes around the armpit and behind the breastbone.
- cN3c means there are cancer cells in the lymph nodes above the collarbone.
Pathological node staging
There are several stages in the pathological node staging. This is a simplified description of the pathological node staging for breast cancer.
pNX means it is not possible to assess the lymph nodes for example, if they were previously removed.
pN0 means there are no cancer cells in any nearby nodes or only small clusters of cancer cells less than 0.2 mm across (isolated tumour cells).
pN1 is divided into 4 groups:
- pN1mi means the cancer cells in the lymph nodes are very small. These are called micrometastases. They are larger than 0.2 mm but are less than 2 mm.
- pN1a means that there are cancer cells in 1 to 3 lymph nodes in the armpit and at least one is larger than 2 mm.
- pN1b means there are cancer cells in the
sentinel lymph nodes behind the breastbone (the internal mammary sentinel nodes). - pN1c means there are cancer cells in 1 to 3 lymph nodes in the armpit and in the sentinel lymph nodes behind the breastbone.
pN2 is divided into 2 groups:
- pN2a means there are cancer cells in 4 to 9 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 breastbone (the internal mammary nodes), which have been seen on a scan or felt by the doctor. There is no evidence of cancer in the lymph nodes in the armpit.
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 2 mm, 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.
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.
cM0(i+) means there is no sign of cancer spread to a different part of the body on physical examination or scans. But cancer cells are present in the blood, , or lymph nodes far away from the breast. The cells are found by laboratory tests.
cM1 means the cancer has spread to another part of the body. This is seen on scans or felt by the doctor.
pM1 means that cancer measuring more than 0.2 mm has spread to another part of the body. This has been confirmed by looking at a tissue sample removed during a biopsy or surgery.
Other tests on the breast cancer cells
Your doctor uses information from a tissue sample of your cancer to find out about the stage. They can also find out other information about your cancer. These include:
- receptors for the
hormones oestrogen and progesterone - levels of the protein HER2 (human epidermal growth factor receptor 2)
- the grade of the cancer
This information helps your doctor work out your overall stage, outlook (prognosis) and treatment plan.
Treatment
The TNM staging helps your doctor decide which treatment you need. Treatment also depends on:
- the type of cells the cancer started in
- whether your cancer cells have receptors for particular cancer drugs
- the grade of the cancer
- whether you have had the
menopause - other health conditions you may have
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 drugs
- bisphosphonates
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