The stage of your breast cancer is a key factor in determining the type of treatment you will receive. At the Abramson Cancer Center, our breast cancer pathologists and radiologists use their expertise to accurately stage breast cancer. The detailed information they provide ensures that you get the most appropriate treatment based on your diagnosis. Learn more about what sets breast cancer stages apart and the criteria used to stage breast cancer at Penn Medicine.
How Is Breast Cancer Staged and Graded?
After a breast cancer diagnosis, doctors assign a cancer stage based on the cancer’s location, tumor size and whether it has spread. Staging directs breast cancer treatment and may be a qualifying factor for some clinical trials.
Breast cancer is staged using advanced breast imaging, breast biopsy and other diagnostic tests. How we stage cancer depends on whether you have had breast cancer surgery. There are two types of staging for breast cancer:
- Clinical staging: We stage cancer prior to surgery. The stage is based on a physical exam, nonsurgical biopsy and breast imaging.
- Pathologic staging: We study tissue removed during breast cancer surgery. For advanced cancer, we also use information obtained from a sentinel lymph node biopsy. Whenever possible, we use pathologic staging, because it provides the most accurate picture of breast cancer.
What is the TNM System for Staging Breast Cancer?
The TNM system for cancer staging refers to an international standard for classifying the malignancy of a tumor based on a list of factors involving the tumor (T), node (N), and metastases (M). The criteria used includes:
- Size of the tumor (T): How large is the area of cancer?
- Spread to lymph nodes (N): Has the cancer spread to nearby lymph nodes?
- Metastasis to distant sites (M): Has the cancer spread to other areas of the body?
- Hormone receptor status: Is it indicative of hormone-positive breast cancer?
- HER2 (human epidermal growth factor receptor 2) status: Is the cancer HER2-positive?
- Grade of the cancer (G): How closely do cancer cells resemble normal cells?
We use this information to determine the most appropriate disease stage. Every breast cancer is unique, making staging a complex process. Your breast cancer team can answer any questions about staging.
T Values for Breast Cancer Staging
As described above, the T in the TNM staging system is used to describe the size of the original breast cancer tumor (T), denoted by the letter T followed by a symbol or number to further indicate how large of an area the primary tumor has taken over. There are seven classifications for the T category for staging breast cancer:
- TX: Original tumor is unable to be evaluated
- T0: There is no evidence of the original tumor
- Tis: In situ (ductal carcinoma in situ or Paget’s disease of the breast with no related tumor)
- T1: Original tumor diameter is less than or equal to 2 centimeters
- T2: Original tumor diameter is between 2 and 5 centimeters
- T3: Original tumor diameter is greater than 5 centimeters
- T4: Original tumor has invaded other organs, like the chest wall or skin
N Values for Breast Cancer Staging
The N category of the TNM staging system is used to indicate if the breast cancer has spread to surrounding lymph nodes (N). This is denoted by the letter N followed by a symbol or number, with a higher number representing a greater number of lymph nodes impacted. There are five classifications for the N category for staging breast cancer:
- NX: Lymph nodes are unable to be evaluated
- N0: There is no spread to nearby lymph nodes
- N1: Cancer has spread to fewer than 3 lymph nodes located on the underarm or has spread to any number of lymph nodes located near the breastbone (internal mammary lymph nodes)
- N2: Cancer has spread to between 4 and 9 lymph nodes of the underarm or has enlarged the lymph nodes of the internal mammary area
- N3 (includes N3a, N3b, and N3c): Cancer has spread to greater than 10 lymph nodes of the underarm, cancer has spread to lymph nodes under the collarbone, cancer has spread to at least 1 underarm lymph node and enlarged breast bone lymph nodes, cancer has spread to at least 4 underarm lymph nodes and detected through biopsy to have spread to the breast bone lymph nodes, OR cancer has spread to lymph nodes above the collarbone on the same side of the body as the cancer
In all N3 scenarios, the spread to the underarm or collar bone lymph nodes must be at least 2 millimeters in size.
M Values for Breast Cancer Staging
M values of the TNM staging system indicate metastases (M), or spread, to distant organs or areas of the body not originally affected by the primary tumor. There are only two classifications for the M category for staging breast cancer, followed either by a 0 or a 1:
- M0: No spread detected in any distant areas of the body via imaging tests
- M1: Spread detected in one or more distant areas of the body, such as the bones or brain, via imaging tests and a biopsy has been done to verify a spread of 0.2 millimeters or more
Stage 0 Breast Cancer
Cancer classified as stage 0 is only located in the breast ducts. It has not spread to surrounding tissue, lymph nodes or distant sites. This stage describes non-invasive types of cancer, such as ductal carcinoma in situ (DCIS).
Stage I Breast Cancer
Stage I cancer is the earliest stage for most types of invasive breast cancer (cancer that has spread to nearby tissue). Most stage I breast tumors are 2 centimeters or smaller, as indicated by the T1 of the TNM staging system. We divide stage I cancer into two categories (IA and IB). More advanced cancer may be classified as either stage IA or IB depending on the cancer’s hormone receptors and HER2-status.
Stage II Breast Cancer
Stage II breast cancer has not spread to distant sites. Stage II cancer is further classified (stage IIA and IIB) depending on the tumor size and any spread to lymph nodes. Cancer in this stage may have spread to lymph nodes under the arm and/or near the breastbone. Even if there is no spread to lymph nodes, cancer is often classified as stage II if the tumor is larger than 2 cm.
Stage III Breast Cancer
All inflammatory breast cancer is classified as stage III. Other types of cancer assigned to stage III may have larger tumors and/or advanced lymph node spread. Cancer that has grown into the chest wall or breast skin is considered stage III. We further classify breast cancer into stage IIIA, IIIB or IIIC. At this stage, the cancer has not spread to distant sites in the body.
Stage IV Breast Cancer
Stage IV breast cancer, commonly called metastatic breast cancer, has spread to distant organs or lymph nodes far from the breast. The most likely areas of spread are the bones, liver, brain and lungs. The initial breast cancer can be any size and may or may not have spread to nearby lymph nodes.
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