Breast cancer can be divided into stages based on the size of the tumor(s) and how much it has spread. Cancers that are large and/or have invaded nearby tissues or organs are at a higher stage than cancers that are small and/or still contained in the breast. To stage breast cancer, doctors need to know:
- if the cancer is invasive or noninvasive
- how large the tumor is
- whether the lymph nodes are involved
- if the cancer has spread to nearby tissue or organs
Breast cancer has 5 main stages: stages 0 to 5.
Stage 0 breast cancer
Stage 0 is DCIS. Cancer cells in DCIS remain confined to the ducts in the breast and have not spread into nearby tissue.
Stage 1 breast cancer
- Stage 1A: The primary tumor is 2 centimeters (cm) wide or less, and the lymph nodes are not affected.
- Stage 1B: Cancer is found in nearby lymph nodes, and either there is no tumor in the breast, or the tumor is smaller than 2 cm.
Stage 2 breast cancer
- Stage 2A: The tumor is smaller than 2 cm and has spread to 1–3 nearby lymph nodes, or it’s between 2 and 5 cm and hasn’t spread to any lymph nodes.
- Stage 2B: The tumor is between 2 and 5 cm and has spread to 1–3 axillary (armpit) lymph nodes, or it’s larger than 5 cm and hasn’t spread to any lymph nodes.
Stage 3 breast cancer
- Stage 3A:
- The cancer has spread to 4–9 axillary lymph nodes or has enlarged the internal mammary lymph nodes, and the primary tumor can be any size.
- Tumors are greater than 5 cm, and the cancer has spread to 1–3 axillary lymph nodes or any breastbone nodes.
- Stage 3B: A tumor has invaded the chest wall or skin and may or may not have invaded up to nine lymph nodes.
- Stage 3C: Cancer is found in 10 or more axillary lymph nodes, lymph nodes near the collarbone, or internal mammary nodes.
Stage 4 breast cancer
Stage 4 breast cancer can have a tumor of any size, and its cancer cells have spread to nearby and distant lymph nodes as well as distant organs. The testing your doctor does will determine the stage of your breast cancer, which will affect your treatment.