Once your health care team knows you have breast cancer, they will do more tests to stage it. Staging is a tool the team uses to find out how advanced the cancer is. The stage of the cancer depends on the size and location of a tumor, whether it has spread, and how far the cancer has spread.

Your health care team uses staging to help:

• Decide the best treatment
• Know what kind of follow-up will be needed
• Determine your chance of recovery (prognosis)
• Find clinical trials you may be able to join

There are two types of staging for breast cancer.

Clinical staging is based on tests done before surgery. These may include:

• Physical exam
• Mammogram
• Breast MRI
• Breast Ultrasound
• Breast Biopsy, either ultrasound or stereotactic
• Chest x-ray
• CT scan
• Bone scan
• PET Scan

Pathological staging uses the results from lab tests done on breast tissue and lymph nodes removed during surgery. This type of staging will help determine additional treatment and help predict what to expect after treatment ends.

Stages of breast cancer are defined by a system called TNM:

• T stands for tumor. It describes the size and location of the main tumor.
• N stands for lymph nodes. It describes whether cancer has spread to the nodes. It also tells how many nodes have cancer cells.
• M stands for metastasis. It tells whether the cancer has spread to parts of the body away from the breast.

Doctors use seven main stages to describe breast cancer.

• Stage 0, also called carcinoma in situ. This is cancer that is confined to the lobules or ducts in the breast. It has not spread to surrounding tissue. Lobules are parts of the breast that produce milk. Ducts carry the milk to the nipple. Stage 0 cancer is called noninvasive. This means it has not spread. Some stage 0 cancers become invasive later. But doctors cannot tell which ones will and which will not.
• Stage I. The tumor is small (or may be too small to see) and invasive. It may or may not have spread to the lymph nodes close to the breast.
• Stage II. There may be no tumor found in the breast, but cancer can be found that has spread to axillary lymph nodes or nodes close to the breastbone. Axillary nodes are nodes found in a chain from under the arm to above the collarbone. There might also be a tumor between 2 and 5 centimeters in the breast with small cancers in some of the lymph nodes. Or, the tumor could be larger than 5 centimeters with no cancer in the nodes.
• Stage IIIA. Cancer has spread to 4 to 9 axillary nodes or to nodes near the breastbone but not to other parts of the body. Or, there could be a tumor larger than 5 centimeters and cancer that has spread to 3 axillary nodes or to nodes near the breastbone.
• Stage IIIB. The tumor has spread to the chest wall or to the skin of the breast causing an ulcer or swelling. It may also have spread to axillary nodes but not to other parts of the body.
• Stage IIIC. Cancer of any size has spread to at least 10 axillary nodes. It may also have spread to the skin of the breast or breast wall, but not to distant parts of the body.
• Stage IV. The cancer is metastatic, which means it has spread to other organs such as the bones, lungs, brain, or liver.

The type of cancer you have, along with the stage, will help determine your treatment. With stage I, II, or III breast cancer, the main goal is to cure the cancer by treating it and keeping it from coming back. With stage IV, the goal is to improve symptoms and prolong life. In almost all cases, stage IV breast cancer cannot be cured.

Cancer can come back after treatment ends. If it does, it can occur in the breast, in distant parts of the body, or in both places. If it does return, it may need to be restaged.

Korourian S, Klimberg VS. Clinical prognosis and staging of breast cancer. In: Klimberg VS, Gradishar WJ, Bland KI, Korourian S, White J, Copeland EM, eds. Bland and Copeland's The Breast. 6th ed. Philadelphia, PA: Elsevier; 2024:chap 26.

National Cancer Institute website. Breast cancer treatment (adult) (PDQ) - health professional version. www.cancer.gov/types/breast/hp/breast-treatment-pdq. Updated January 19, 2024. Accessed April 4, 2024.