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Breast Cancer Stages
If you are diagnosed with breast cancer, your cancer care team will try to figure out if it has spread, and if so, how far. This process is called staging. The stage of a cancer describes how much cancer is in the body. It helps determine how serious the cancer is and how best to treat it.
Doctors use a cancer's stage when talking about survival statistics.
What are the breast cancer stages?
The stage of breast cancer is based on the results of tests such as physical exams, imaging, and biopsies.
The earliest stage breast cancers are stage 0 (carcinoma in situ). Then, they range from stage I through IV. As a rule, the lower the number, the less the cancer has spread. Within a stage, an earlier letter means a lower stage.
Although each person’s cancer experience is unique, cancers with similar stages tend to have a similar outlook and are often treated in a similar way.
How is the stage determined?
The staging system most often used for breast cancer is the American Joint Committee on Cancer (AJCC) TNM system. Doctors use 7 key pieces of information:
- Size of the primary tumor (T) describes the size of the main (primary) tumor and if it has grown into nearby areas.
- Lymph node spread (N) describes the extent of spread to nearby (regional) lymph nodes.
- Metastasis (M) indicates if the cancer has metastasized (spread) to other organs of the body, such as the bones, liver, lungs, or brain.
- Grade (G) describes how quickly the tumor is likely to grow. Low-grade tumor cells look more like normal cells and are less likely to grow and spread quickly. High-grade tumor cells look more abnormal and are likely to grow faster.
- Estrogen receptor (ER) status indicates whether the cancer cells have proteins called estrogen receptors.
- Progesterone receptor (PR) status indicates whether the cancer cells have proteins called progesterone receptors.
- HER2 status indicates whether the cancer cells make too much of the HER2 protein.
In addition, Oncotype DX® Recurrence Score results might also be considered in the stage in certain situations.
Once all these factors have been determined, this information is combined in a process called stage grouping to assign an overall stage. For more information see Cancer Staging.
Details about the first 3 factors (the TNM categories) are below. However, the addition of information about ER, PR, and HER2 status along with grade has made stage grouping for breast cancer more complex than for other cancers. Because of this, it is best to ask your doctor about your specific stage and what it means.
Details of the TNM staging system
The staging system most often used for breast cancer is the American Joint Committee on Cancer (AJCC) TNM system. The most recent AJCC system, effective January 2018, has both clinical and pathologic staging systems for breast cancer.
The pathologic stage, also called the surgical stage, is determined by examining tissue removed during an operation.
If surgery is not possible right away or at all, the cancer will be given a clinical stage instead. This is based on the results of a physical exam, biopsy, and imaging tests. In some cases, the cancer has spread further than the clinical stage estimates and might not predict your outlook as accurately as a pathologic stage.
The categories below use the pathologic (surgical) definitions.
T categories for breast cancer
T followed by a number from 0 to 4 describes the main (primary) tumor's size and if it has spread to the skin or to the chest wall under the breast. Higher T numbers mean a larger tumor or wider spread to tissues near the breast.
- TX: Primary tumor cannot be assessed.
- T0: No evidence of primary tumor.
- Tis: Carcinoma in situ (DCIS, or Paget disease of the nipple with no associated tumor mass).
- T1: Includes T1a, T1b, and T1c. Tumor is 2 cm (3/4 of an inch) or less across.
- T2: Tumor is more than 2 cm but not more than 5 cm (2 inches) across.
- T3: Tumor is more than 5 cm across.
- T4: Includes T4a, T4b, T4c, and T4d. Tumor of any size growing into the chest wall or skin. This includes inflammatory breast cancer.
N categories for breast cancer
N followed by a number from 0 to 3 indicates whether the cancer has spread to lymph nodes near the breast and, if so, how many lymph nodes are involved.
Lymph node staging for breast cancer is based on how the nodes look under the microscope. Newer methods have made it possible to find even smaller groups of cancer cells, but experts haven't been sure how much these tiny deposits of cancer cells influence outlook.
Types of lymph node metastases
Cancer that has spread to the lymph nodes (metastases) is classified as:
- Macrometastases, which are larger than 2 mm wide
- Micrometastases, which are 0.2 mm (or 200 cells) to 2 mm wide
- Isolated tumor cells, which are even smaller areas of cancer spread found using lab tests.
Micrometastases are counted only if there aren't any larger areas of cancer spread. In some cases, even smaller areas of cancer cells are found, but it is not clear if these smaller areas affect the outlook, and they don’t change the N stage. When these smaller areas are found, it is noted with an i+ or mol+ next to N0.
Nearby lymph nodes cannot be assessed (for example, if they were removed previously).
Cancer has not spread to nearby lymph nodes.
- N0(i+): An area of isolated tumor cells containing fewer than 200 cells and smaller than 0.2 mm was seen using routine tissue stains or immunohistochemistry.
- N0(mol+): Cancer cells cannot be seen in underarm lymph nodes but traces of cancer cells were detected using RT-PCR (a molecular test that can find very small amounts of cancer).
Cancer has spread to 1 to 3 axillary (underarm) lymph nodes, and/or cancer is found in internal mammary lymph nodes (those near the breastbone) on sentinel lymph node biopsy.
- N1mi: Micrometastases are in the lymph nodes under the arm that are at least 0.2 mm across but not larger than 2 mm.
- N1a: Cancer has spread to 1 to 3 lymph nodes under the arm with at least one area of cancer spread greater than 2 mm across.
- N1b: Cancer has spread to internal mammary lymph nodes on the same side as the cancer, but this spread could only be found on sentinel lymph node biopsy and it did not cause the lymph nodes to become enlarged.
- N1c: Both N1a and N1b apply.
Cancer has spread to 4 to 9 lymph nodes under the arm, or cancer has enlarged the internal mammary lymph nodes.
- N2a: Cancer has spread to 4 to 9 lymph nodes under the arm, with at least one area of cancer spread larger than 2 mm.
- N2b: Cancer has spread to one or more internal mammary lymph nodes, causing them to become enlarged.
N3a: Cancer has spread to 10 or more axillary lymph nodes, with at least 1 area of cancer spread greater than 2 mm. Or, cancer has spread to the lymph nodes under the collarbone (infraclavicular nodes), with at least 1 area of cancer spread greater than 2 mm.
N3b: Cancer is found in at least 1 axillary lymph node with at least 1 area of cancer spread greater than 2 mm and has enlarged the internal mammary lymph nodes. Or, cancer has spread to 4 or more axillary lymph nodes, with at least one area of cancer spread greater than 2 mm, and to the internal mammary lymph nodes on sentinel lymph node biopsy.
N3c: Cancer has spread to the lymph nodes above the collarbone (supraclavicular nodes) on the same side of the cancer with at least one area of cancer spread greater than 2 mm.
M categories for breast cancer
M followed by a 0 or 1 indicates whether the cancer has spread to distant organs such as the lungs, liver, or bones.
- M0: No distant spread is found on x-rays (or other imaging tests) or by physical exam.
- cM0(i+): Small numbers of cancer cells are found in blood or bone marrow by special tests, or tiny areas of cancer spread no larger than 0.2 mm are found in lymph nodes away from the underarm, collarbone, or internal mammary areas.
- M1: Cancer has spread to distant organs as seen on imaging tests or by physical exam, or a biopsy of one of these areas proves cancer has spread and is larger than 0.2 mm.
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- References
Developed by the American Cancer Society medical and editorial content team with medical review and contribution by the American Society of Clinical Oncology (ASCO).
American Joint Committee on Cancer. Breast. In: AJCC Cancer Staging Manual. 8th ed. New York, NY: Springer; 2017:589.
Giuliano AE, Connolly JL, Edge SB, et al. Breast Cancer-Major changes in the American Joint Committee on Cancer eighth edition cancer staging manual. CA Cancer J Clin. 2017;67(4):290-303.
Joe BN. Clinical features, diagnosis, and staging of newly diagnosed breast cancer. UpToDate. 2026. Accessed at https://www.uptodate.com/contents/clinical-features-diagnosis-and-staging-of-newly-diagnosed-breast-cancer on March 18, 2026.
National Comprehensive Cancer Network. NCCN Clinical Practice Guidelines in Oncology: Invasive Breast Cancer Version 2.2026 – February 27, 2026. Accessed at https://www.nccn.org/professionals/physician_gls/pdf/breast.pdf on April 2, 2026.
Last Revised: July 23, 2026
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