Stages of breast cancer

Your stage of breast cancer refers to how extensive the cancer is, on a scale from stage 0 to stage IV.

Your doctor determines your stage of breast cancer through examination of the tissue removed during a mastectomy or lumpectomy and of the lymph nodes under your arm (axillary lymph nodes).

Staging your cancer gives your doctor an idea of your prognosis — the likely outcome of your disease — and helps guide treatment decisions. The 0 to 4 staging system, based on data from large numbers of people with breast cancer, estimates your chance of surviving for at least five years after your diagnosis. The numbers express probability, not certainty. With advances in detection and treatment, people with breast cancer are living longer than ever before.