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 or lobules of the breast. It has not spread to the surrounding tissue. It is also called noninvasive cancer.

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

• Stage IA: The tumor is small. It has not spread to the lymph nodes (T1, N0, M0).
• Stage IB: The tumor is in the lymph nodes and may also be in the breast tissue. It is less than 2 cm in size

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

• Stage IIA: A tumor may not be found in the breast or there is a tumor that is 2cm or smaller 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 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 of any size has spread to 4 to 9 lymph nodes. Or the tumor is larger than 5cm and only has spread to 1-3 lymph nodes.
• 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: The tumor may be any size with spread to 10 or more lymph nodes.

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.

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 99 percent. This is the number of people in a treatment group who are alive 5 years after they were diagnosed¹⁵

About 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.