After surgery, the pathology report will provide information for staging the cancer. Staging identifies how advanced the cancer is, and thus helps determine whether you'll need further treatment after surgery and predicts the outlook for a cure. As well, staging allows physicians from around the world to compare and contrast the results of treatments. Without a staging system, there would be no meaningful comparisons among different centers that treat patients with breast cancer.

In the past, staging was denoted by the letters A, B, C and D. However, today, staging is done with the TNM system:

• T Stage — Refers to the size of the primary tumor
• N Stage — Refers to whether the cancer has spread to the draining lymph nodes
• M Stage — Refers to whether the cancer has spread to areas away from the breast (for example, the liver, bones or brain)

Every cancer, including breast cancer, is classified with the TNM system. Because the TNM criteria can differ greatly, they can be further staged as follows.

Stage O: Carcinoma in situ. Cancer has not spread beyond the ducts in the breast.

Stage I: The tumor is two centimeters (a little less than one inch) or less in diameter and it has not spread to the underarm (axillary) lymph nodes or to any other sites.

Stage II: Tumor is larger than two centimeters, or cancer cells are detected in movable (not fixed) axillary lymph nodes on the same side of the body as the breast mass. If the cancer-containing lymph nodes are fixed meaning they are attached to the skin or underlying tissue then the cancer is stage III.

Stage III: The tumor may be any size, but it has spread to fixed lymph nodes. If a tumor involves the skin or chest wall or has spread to the lymph nodes located underneath the breast on the same side of the body as the tumor, it automatically is at least stage III, no matter what the size.

Stage IV: Any tumor that has spread to any other site beyond the local area of the breast (for example, to internal organs or bones), no matter what the size.

The lower the stage, the better the outlook for survival.

But staging can be complicated. Speak to your physician if you have been diagnosed with breast cancer.