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:
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 II describes invasive breast cancer. There are 2 types:
Stage III describes invasive breast cancer. There are 3 types:
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.