If you want more information about how the stage of a breast cancer is determined, this is the right place. If you already know the stage of your cancer, this page will explain what your doctors are basing that determination on. There is a difference between what’s called “clinical” and “pathologic” stage that will be explained below. If you haven’t yet had definitive surgical treatment (that is, you’ve only had a biopsy), then your doctors will be making a clinical stage assessment. After the surgery, the stage is revised if needed, based on the additional information provided from the evaluation of the tissue removed.

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What does “cancer stage” mean, and how is it determined?

The method of staging cancers has been well-defined for decades. There is a standard manual that has been agreed upon by virtually the entire international community of cancer experts, which is used as a reference. This manual is updated every few years. The idea is to try to categorize cancers into smaller groups that are likely to behave in similar fashion. This grouping of similar cancers allows doctors to provide more individualized treatment plans. Rather than treating all cancers the same, each stage may be treated in a way that will best fit that subgroup of cancers. The concept of staging is essential in making the best decisions about treatment. Your surgeon should determine the stage of your cancer at the outset, based on what can be learned about your cancer from physical examination, from biopsy information, and from any imaging studies that might have been done. This is called a clinical stage. Once a definitive operation has been done, the added information from the surgery will then be used to revise the cancer stage if needed. This is called a pathologic stage. Now, how does the staging system work? For nearly all different cancer types, the stage depends on just three things, summarized by the initials TNM. These stand for: (1) T is for tumor size, (2) N is for lymph node status, and (3) M stands for evidence of metastatic disease, or in other words, cancer spread beyond the lymph nodes. Not surprisingly, this is called the

TNM staging system. The group which publishes the guidelines is call the American Joint Committee on Cancer. Most of you will not need any more detailed information on this but the link is there if you are interested in learning more.


For breast cancer, the T part of the stage is determined as shown:

Tumor Size (invasive component) T
DCIS, non-invasive (cancer “seeds”) 0
0 -2 cm 1
>2-5 cm 2
> 5 cm 3
Ulcerating the overlying skin, or growing into the chest muscles 4


The N part of the stage is determined as shown:

Lymph node status (in the axilla, or armpit) N
No lymph nodes with cancer 0
1-3 lymph nodes with cancer 1
4 –9 lymph nodes with cancer 2
10 or more nodes and some other advanced findings 3


The M part of the stage is determined as shown:

Is metastatic disease present? M
No 0
Yes (typically might be in liver, lungs, bone, or brain) 1


Once each of these factors is determined, the three numbers are combined into a Stage. I will keep it simple at this point and just say that the higher the numbers, the higher the stage. If you want the entire summary of assessing the stage, here is a link to the American Cancer Society’s website that gives these details.

If you would like to read more about treatment specific for a given stage of breast cancer, follow the links below. Or you can go back to the breast cancer page to decide what other information to review.


Stage 0 Stage 1 Stage 2  Stage 3  Stage 4


As we learn more about breast cancer, we may find even better ways to categorize them. We already have a few extremely important tests by which we further categorize each cancer, based on the presence or absence of certain proteins or genes in the cancer cells. These tests include estrogen and progesterone receptors, and HER2. These tests are very important because, if the tests are positive, then we know there is a high likelihood of benefit from very specific treatment, and if the tests are negative, we know that using these targeted treatments would be of no benefit at all. As other similar tests become available, it may be that we will rely less on the TNM staging, and rely more and more on specific genetic characteristics which give high predictability of response to matching targeted treatments.

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