If breast cancer is diagnosed, the doctor needs to know the stage of the disease to plan the best treatment.

Staging is a methodical approach to determine if the cancer has spread, and if so, to what parts of the body. The American Joint Committee on Cancer (AJCC) TNM staging system is the most common system used to stage breast cancer.

Stages are classified as Roman numerals I-IV (1-4). The higher the number, the more the disease has spread.

Updated June 3, 2015