The Stages of Breast Cancer

Staging breast cancer is a way of measuring how much cancer is in your body. In addition to other factors, such as your age, general health and blood test results, your physicians will use the stage of your breast cancer to best decide the treatment options to discuss with you.

Breast cancer staging is determined by two factors:

  • Tumor size (measured in centimeters)
  • Tumor site (whether it has spread)

Stage 0 (Carcinoma in Situ)

Stage 0 breast cancer is considered non-invasive (in situ), meaning that the cancer is still confined within breast ducts or lobules and has not yet spread to surrounding tissues. Stage 0 cancer is classified as either:

  • Ductal carcinoma in situ (DCIS). These are cancer cells in the lining of a duct that have not invaded the surrounding breast tissue.
  • Lobular carcinoma in situ (LCIS). These are cancer cells in the lobules of the breast. LCIS rarely develops into invasive breast cancer, but having it in one breast increases the risk of developing cancer in the other breast.

Stage 1 and 2 (Early-Stage Invasive)

In stage 1 cancer, cancer cells have not spread beyond the breast, and the tumor is no more than 2 cm (about 3/4 of an inch) across.

Stage 2 cancer is classified as either stage 2A or stage 2B.

In stage 2A cancer the tumor is either:

  • No more than 2 centimeters and has spread to the underarm lymph nodes (axillary lymph nodes)
  • Between 2 - 5 centimeters and has not spread to the underarm lymph nodes

In stage 2B cancer the tumor is either:

  • Larger than 2 centimeters and less than 5 centimeters and has spread to 1 - 3 axillary lymph nodes
  • Larger than 5 centimeters but has now spread to lymph nodes

Stage 3 (Locally Advanced)

Stage 3 breast cancer is classified into several sub-categories: Stage 3A, stage 3B, and stage 3C (operable or inoperable).

In stage 3A breast cancer, the tumor is either of the following:

  • Not more than 5 centimeters and has spread to 4 - 9 axillary lymph nodes
  • Larger than 5 centimeters and has spread to 1 - 9 axillary nodes or to internal mammary nodes.

In stage 3B breast cancer, the tumor has spread to either of the following:

  • Tissues near the breast (including the skin or chest wall)
  • Lymph nodes within the breast or under the arm

Stage 3C breast cancer is classified as either operable or inoperable.

In operable stage 3C, the cancer may be found in:

  • 10 or more of the underarm lymph nodes
  • Lymph nodes beneath the collarbone and near the neck on the same side of the body as the affected breast
  • Lymph nodes within the breast as well as underarm lymph nodes

In inoperable stage 3 breast cancer, the cancer has spread to lymph nodes above the collarbone and near the neck on the same side of the body as the affected breast.

Stage 4 (Advanced Cancer)

In stage 4, the cancer has spread (metastasized) from the breast to other parts of the body. In about 75 percent of cases, the cancer has spread to the bone. The cancer at this stage is considered to be chronic and incurable, and the usefulness of treatments is limited. The goals of treatment for stage 4 cancer are to stabilize the disease and slow its progression, as well as to reduce pain and discomfort.

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