Slide show: Stages of breast cancer

Your stage of breast cancer refers to how extensive your breast cancer is. This includes both the size of the tumor and whether or not any cancer cells have spread from the breast to other areas of your body, including your lymph nodes. Your doctor will determine your stage of breast cancer at the time he or she removes your cancer during a mastectomy or lumpectomy and through close examination of the lymph nodes under your arm.

Your stage of breast cancer can be as low as stage 0 or as high as stage IV. The higher the stage, the larger the tumor or the more the cancer has spread. Stage 0 cancer, for instance, indicates a non-invasive breast cancer that is contained within the duct and hasn't spread within the breast. Some doctors consider stage 0 cancer not a true cancer at all but a predictor of breast cancer.

You have stage I breast cancer if:

• Your tumor is no more than 2 centimeters (cm) in diameter (slightly less than 1 inch).
• The cancer hasn't spread to your lymph nodes.
• The cancer hasn't spread to a distant part of your body.

The five-year survival rate for women treated for stage I breast cancer is 98 percent.

With stage II breast cancer, the tumor size is larger than that of stage I, but the cancer hasn't spread to a distant part of your body. If your cancer is stage II, one of the following is true:

• Your tumor is 2 to 5 cm in diameter. The cancer may or may not have spread to your axillary lymph nodes.
• Your tumor is more than 5 cm in diameter, but the cancer hasn't spread to your axillary lymph nodes (A).
• Your tumor is less than 2 cm in diameter, but the cancer has spread to less than four of your underarm (axillary) lymph nodes (B).

The five-year survival rate for women treated for stage II breast cancer is 76 percent to 88 percent. Because this statistic is based on women diagnosed many years ago and breast cancer treatment since then has improved, the current five-year survival rate may actually be higher.

If you have stage III breast cancer, known as locally advanced cancer, your cancer has spread to the lymph nodes near your breast — those located under your arm or by your collarbone — but not to more distant parts of your body. Here are some examples:

• You may have a tumor that's larger than 5 cm, with cancer cells that have spread to your axillary lymph nodes. However, the nodes aren't growing into one another (A).
• Your tumor is smaller than 5 cm, but the cancer has spread to the axillary lymph nodes above your collarbone (B).

Inflammatory breast cancer, in which the cancer has spread to the breast skin, causing swelling and redness, is classified as stage III breast cancer.

The five-year survival rate for women treated for stage III breast cancer is 49 percent to 56 percent or slightly higher.

Stage IV represents the most advanced form of breast cancer — cancer cells have spread to distant parts of your body, such as bones, organs or lymph nodes located far from your breast. Treatment may help shrink or control the cancer for a while, but it usually won't completely cure the cancer. At this stage, symptom relief becomes a priority.