Staging

Breast cancer staging is an important part of the pathology report that takes into consideration whether your cancer is invasive (cancer cells have broken through to the surrounding tissues), the size of your tumour, whether the cancer has spread to the nearby lymph nodes and whether the cancer has spread to other areas in your body. It is used most commonly to guide treatment decisions.

Certain terms are often used to discuss the stages of breast cancer. Most typically this includes:

Local - describes cancers remaining within the breast.

Regional - cancers with nearby lymph node involvement.

Distant - describes cancers that have spread to other parts of the body.

Breast cancer is staged using the ‘TNM’ system, which stands for Tumour, Nodes and Metastases. This system considers the size of the tumour, the number of lymph nodes that are affected, if any, and the other parts of the body to which the cancer has spread (metastasized), if any.  Based on this information it is given a stage 0-IV.  For example, a classification of T1N0M0 means a small, early-stage breast cancer with no lymph node involvement and no metastases (stage I). A classification of T4N3M1 means an advanced metastatic breast cancer with a large tumour in the breast and cancer in many lymph nodes (stage IV).

• Stage 0 means that the cancer cells are non-invasive (cancer cells have not broken through to the normal surrounding tissues) and have not spread.
   
• Stage I involves a small local (remaining within the breast) invasive tumour without lymph node involvement.
   
• Stage II describes invasive, larger tumours which may involve spread to the nearest lymph nodes.
   
• Stage III indicates invasive cancers with considerable lymph node involvement.
   
• Stage IV means the cancer has spread to other parts of the body (metastasized).

Metastatic breast cancer, also known as advanced, or Stage IV breast cancer, is the spread of cancerous cell growth to areas of the body other than the breast where the cancer first formed. Close to 1,200 Canadian women will receive an initial diagnosis of metastatic breast cancer each year. Some women who had an initial diagnosis of an earlier stage of breast cancer will go on to develop metastatic breast cancer. The risk of this is highly individual and depends on various clinical and pathological features of the initial tumour. Unfortunately, at this time there are no current statistics in Canada to indicate how many people progress from early stage to metastatic.

Metastasis, or the spreading of cancer to a distant location in the body, can happen before or after treatment of the cancer in the breast. It may be the result of a recurrence of breast cancer (breast cancer that returns following a period where it could not be detected). Though breast cancer cells can spread to almost any part of the body, they most commonly spread to the bones. Other common sites include the lungs, liver, brain and skin. It is this distant site of breast cancer that is called a metastasis.

Visit our Living with Metastatic Breast Cancer section to better understand your diagnosis. Our recently updated and re-written Metastatic Breast Cancer Handbook: A guide for individuals living with stage IV breast cancer offers a deeper look at how metastatic breast cancer affects your daily life and provides ways to help manage the changes that it brings.

If you have additional questions about breast cancer staging in relation to your breast cancer, connect with your doctor. 

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