Breast cancer stages

Breast cancer stages range from 0 to IV, with many subcategories. Lower numbers indicate earlier stages of cancer, while higher numbers reflect late-stage cancers.

Stage 0

This stage describes noninvasive (in situ) breast cancer. Ductal carcinoma in situ (DCIS) is an example of stage 0 cancer.

Stage I

This stage is an early stage of invasive breast cancer in which:

• The tumor measures no more than 2 centimeters (cm), or about 3/4 inch, in diameter.
• No lymph nodes are involved — the cancer hasn't spread outside the breast.

Stage II

This stage describes invasive breast cancers in which one of the following is true:

• The tumor measures less than 2 cm (about 3/4 inch) in diameter but has spread to lymph nodes under the arm.
• No tumor is found in the breast, but breast cancer cells are found in lymph nodes under the arm.
• The tumor is between 2 and 5 cm (about 3/4 to 2 inches) in diameter and may or may not have spread to lymph nodes under the arm.
• The tumor is larger than 5 cm (2 inches) in diameter but hasn't spread to any lymph nodes.

Stage III

Stage III breast cancers are subdivided into three categories — IIIA, IIIB and IIIC — based on a number of criteria. By definition, stage III cancers haven't spread to distant sites.

For example, a stage IIIA tumor is larger than 5 cm (2 inches) and has spread to one to three lymph nodes under the arm. Other stage IIIA tumors may be any size and have spread into multiple lymph nodes. The lymph nodes clump and attach to one another or to the surrounding tissue.

In stage IIIB breast cancer, a tumor of any size has spread to tissues near the breast — the skin and chest muscles — and may have spread to lymph nodes within the breast or under the arm. Stage IIIB also includes inflammatory breast cancer, an uncommon but aggressive type of breast cancer.

Stage IIIC cancer is a tumor of any size that has spread:

• To 10 or more lymph nodes under the arm
• To lymph nodes above or beneath the collarbone and near the neck
• To lymph nodes within the breast itself and to lymph nodes under the arm

Stage IV

Stage IV breast cancer has spread to distant parts of the body, such as the lungs, liver, bones or brain.