Stage is usually expressed as a number on a scale of 0 through IV — with stage 0 describing non-invasive cancers that remain within their original location and stage IV describing invasive cancers that have spread outside the breast to other parts of the body.
Understanding Breast Cancer Stages
Your pathology report will include information about the stage of the breast cancer — that is, whether it is limited to one area in the breast, or it has spread to healthy tissues inside the breast or to other parts of the body. Your doctor will begin to determine this during surgery to remove the cancer and look at one or more of the underarm lymph nodes, which is where breast cancer tends to travel first. He or she also may order additional blood tests or imaging tests if there is reason to believe the cancer might have spread beyond the breast.
Cancer stage is based on four characteristics:
- the size of the cancer
- whether the cancer is invasive or non-invasive
- whether cancer is in the lymph nodes
- whether the cancer has spread to other parts of the body beyond the breast
You also may see or hear certain words used to describe the stage of the breast cancer:
- Local: The cancer is confined within the breast.
- Regional: The lymph nodes, primarily those in the armpit, are involved.
- Distant: The cancer is found in other parts of the body as well.
Sometimes doctors use the term “locally advanced” or “regionally advanced” to refer to large tumors that involve the breast skin, underlying chest structures, changes to the breast's shape, and lymph node enlargement that is visible or that your doctor can feel during an exam.
The stage of the breast cancer can help you and your doctor understand your prognosis (the most likely outcome of the disease) and make decisions about treatment, along with all of the other results in your pathology report. Cancer stage also gives everyone a common way to describe the breast cancer, so that the results of your treatment can be compared and understood relative to that of other people.
Your doctor may use another staging system known as TNM to describe the cancer. This system is based on the size of the tumor (T), lymph node involvement (N), and whether the cancer has spread, or metastasized, to other parts of the body (M). TNM is discussed later in this section.
Stage 0 is used to describe non-invasive breast cancers, such as DCIS (ductal carcinoma in situ). In stage 0, there is no evidence of cancer cells or non-cancerous abnormal cells breaking out of the part of the breast in which they started, or getting through to or invading neighboring normal tissue.
Stage I describes invasive breast cancer (cancer cells are breaking through to or invading normal surrounding breast tissue) Stage I is divided into subcategories known as IA and IB.
Stage IA describes invasive breast cancer in which:
- the tumor measures up to 2 centimeters AND
- the cancer has not spread outside the breast; no lymph nodes are involved
Stage IB describes invasive breast cancer in which:
- there is no tumor in the breast; instead, small groups of cancer cells – larger than 0.2 millimeter but not larger than 2 millimeters – are found in the lymph nodes OR
- there is a tumor in the breast that is no larger than 2 centimeters, and there are small groups of cancer cells – larger than 0.2 millimeter but not larger than 2 millimeters – in the lymph nodes
Microscopic invasion is possible in stage I breast cancer. In microscopic invasion, the cancer cells have just started to invade the tissue outside the lining of the duct or lobule, but the invading cancer cells can't measure more than 1 millimeter.
Stage II is divided into subcategories known as IIA and IIB.
Stage IIA describes invasive breast cancer in which:
- no tumor can be found in the breast, but cancer (larger than 2 millimeters) is found in 1 to 3 axillary lymph nodes (the lymph nodes under the arm) or in the lymph nodes near the breast bone (found during a sentinel node biopsy) OR
- the tumor measures 2 centimeters or smaller and has spread to the axillary lymph nodes OR
- the tumor is larger than 2 centimeters but not larger than 5 centimeters and has not spread to the axillary lymph nodes
Stage IIB describes invasive breast cancer in which:
- the tumor is larger than 2 centimeters but no larger than 5 centimeters; small groups of breast cancer cells -- larger than 0.2 millimeter but not larger than 2 millimeters -- are found in the lymph nodes OR
- the tumor is larger than 2 centimeters but no larger than 5 centimeters; cancer has spread to 1 to 3 axillary lymph nodes or to lymph nodes near the breastbone (found during a sentinel node biopsy) OR
- the tumor is larger than 5 centimeters but has not spread to the axillary lymph nodes
Stage III is divided into subcategories known as IIIA, IIIB, and IIIC.
Stage IIIA describes invasive breast cancer in which either:
- no tumor is found in the breast or the tumor may be any size; cancer is found in 4 to 9 axillary lymph nodes or in the lymph nodes near the breastbone (found during imaging tests or a physical exam) OR
- the tumor is larger than 5 centimeters; small groups of breast cancer cells (larger than 0.2 millimeter but not larger than 2 millimeters) are found in the lymph nodes OR
- the tumor is larger than 5 centimeters; cancer has spread to 1 to 3 axillary lymph nodes or to the lymph nodes near the breastbone (found during a sentinel lymph node biopsy)
Stage IIIB describes invasive breast cancer in which:
- the tumor may be any size and has spread to the chest wall and/or skin of the breast and caused swelling or an ulcer AND
- may have spread to up to 9 axillary lymph nodes OR
- may have spread to lymph nodes near the breastbone
Inflammatory breast cancer is considered at least stage IIIB. Typical features of inflammatory breast cancer include:
- reddening of a large portion of the breast skin
- the breast feels warm and may be swollen
- cancer cells have spread to the lymph nodes and may be found in the skin
Stage IIIC describes invasive breast cancer in which:
- there may be no sign of cancer in the breast or, if there is a tumor, it may be any size and may have spread to the chest wall and/or the skin of the breast AND
- the cancer has spread to 10 or more axillary lymph nodes OR
- the cancer has spread to lymph nodes above or below the collarbone OR
- the cancer has spread to axillary lymph nodes or to lymph nodes near the breastbone
Stage IV describes invasive breast cancer that has spread beyond the breast and nearby lymph nodes to other organs of the body, such as the lungs, distant lymph nodes, skin, bones, liver, or brain.
You may hear the words “advanced” and “metastatic” used to describe stage IV breast cancer. Cancer may be stage IV at first diagnosis or it can be a recurrence of a previous breast cancer that has spread to other parts of the body.
Learn about what treatments you can generally expect according to cancer stage in the Options by Cancer Stage section in Planning Your Treatment.
TNM staging system
TNM (Tumor, Node, Metastasis) is another staging system researchers use to provide more details about how the cancer looks and behaves. Your doctor might mention the TNM classification for your case, but he or she is much more likely to use the numerical staging system. Sometimes clinical trials require TNM information from participants, so talk to your doctor if you are considering participation in a clinical trial.
The TNM system is based on three characteristics:
- size (T stands for tumor)
- lymph node involvement (N stands for node)
- whether the cancer has metastasized (M stands for metastasis), or moved beyond the breast to other parts of the body.
The T (size) category describes the original (primary) tumor:
- TX means the tumor can't be measured or found.
- T0 means there isn't any evidence of the primary tumor.
- Tis means the cancer is "in situ" (the tumor has not started growing into healthy breast tissue).
- T1, T2, T3, T4: These numbers are based on the size of the tumor and the extent to which it has grown into neighboring breast tissue. The higher the T number, the larger the tumor and/or the more it may have grown into the breast tissue.
The N (lymph node involvement) category describes whether or not the cancer has reached nearby lymph nodes:
- NX means the nearby lymph nodes can't be measured or found.
- N0 means nearby lymph nodes do not contain cancer.
- N1, N2, N3: These numbers are based on the number of lymph nodes involved and how much cancer is found in them. The higher the N number, the greater the extent of the lymph node involvement.
The M (metastasis) category tells whether or not there is evidence that the cancer has traveled to other parts of the body:
- MX means metastasis can't be measured or found.
- M0 means there is no distant metastasis.
- M1 means that distant metastasis is present.
Once the pathologist knows your T, N, and M characteristics, he or she can use them to assign a stage to the cancer. For example, a T1 N0 M0 breast cancer would mean that the primary breast tumor is less than 2 centimeters across (T1), has not involved the lymph nodes (N0), and has not spread to distant parts of the body (M0). This cancer would be grouped as stage I.
For more detailed information on the TNM staging system and how it relates to the numerical stage, visit the American Cancer Society’s section on breast cancer staging.
Your Guide to the Breast Cancer Pathology Report is an on-the-go reference booklet you can fill out with your doctor or nurse to keep track of the results of your pathology report. Download the PDF of the booklet to print it at home.