What are the stages of breast cancer?

In order to determine the most effective treatment options, breast cancer is staged based on physical exam, biopsy and imaging results. Stage I cancer involves tumors smaller than two centimeters that have not spread outside the breast. Stage II cancer involves tumors less than five centimeters that may have spread to nearby lymph nodes. Stage III cancer involves tumors greater than five centimeters or that have grown into the skin or other tissues surrounding the breast. Stage III cancer may also involve nearby lymph nodes. Stage IV cancer has spread to other areas of the body, commonly bone, lungs, or liver.