Breast Cancer Staging

The stage of your cancer is based on the size of the tumor and if it has spread to other areas.¹⁴ It is also based on the type of tumor cells (genes and biomarkers—see Genetic and Biomarker Testing).

There are five stages of breast cancer, including zero through four, written as 0, I, II, III, and IV. The higher the number, the more the cancer has spread. The cancer is staged when you are first diagnosed. If you have Stage II breast cancer and the cancer comes back and spreads to your bone, you will still be Stage II breast cancer with metastasis (spread) to the bones.¹³

The stage of breast cancer is also described by the "TNM" system:

• T: Tumor size (in centimeters)
• N: Number of near by lymph nodes with cancer
• M: Whether the cancer has metastasized or spread to other organs of the body (0 = no spread, 1 = it has spread)

Stage 0: The disease is only in the ducts and lobules of the breast. It has not spread to the surrounding tissue. It is also called noninvasive cancer (Tis, N0, M0).

Stage I: The disease is invasive. Cancer cells are now in normal breast tissue. There are 2 types:

• Stage IA: The tumor is up to 2 centimeters (cm). It has not spread to the lymph nodes (T1, N0, M0).
• Stage IB: The tumor is in the breast and is less than 2 cm. Or the tumor is in the lymph nodes of the breast and there is no tumor in the breast tissue.

Stage II describes invasive breast cancer. There are 2 types:

• Stage IIA: A tumor may not be found in the breast, but cancer cells have spread to at least 1 to 3 lymph nodes. Or Stage IIA may show a 2 to 5 cm tumor in the breast with or without spread to the axillary lymph nodes.
• Stage IIB: The tumor is 2 to 5 cm and the disease has spread to 1 to 3 axillary lymph nodes. Or the tumor is larger than 5 cm but has not spread to the axillary lymph nodes.

Stage III describes invasive breast cancer. There are 3 types:

• Stage IIIA: The tumor is in the breast and any size or no tumor is found in the breast but is in the lymph nodes. The disease has spread to more than 4 lymph nodes in the breast or axilla. It has not spread to other parts of the body.
• Stage IIIB: The tumor may be any size and the disease has spread to the chest wall. It may cause swelling of the breast and may be in up to 9 lymph nodes. Inflammatory breast cancer is considered Stage IIIB.
• Stage IIIC: There may be no sign of cancer in the breast or a tumor may be any size and may have spread to the chest wall or breast skin. The disease has spread to 10 or more axillary lymph nodes, or nodes above or below the collarbone or next to the breastbone.

Stage IV (metastatic): The tumor can be any size and the disease has spread to other organs and tissues, such as the bones, lungs, brain, liver, distant lymph nodes, or chest wall (any T, any N, M1).

63 percent of female breast cancers are found at the local stage. The cancer is in the primary site and has not spread (metastasized).

The 5-year survival rate for local breast cancer is 98.9 percent. This is the number of people in a treatment group who are alive 5 years after they were diagnosed¹⁵

About 5 to 6 percent of women with breast cancer first find it after it has spread.¹⁶

See the BreastCancer.org pathology report guide for more information.