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Breast Cancer Stages

Stage is usually expressed as a number on a scale of 0 through IV — with stage 0 describing non-invasive cancers that remain within their original location and stage IV describing invasive cancers that have spread outside the breast to other parts of the body.

Cancer stage is based on four characteristics:

  • the size of the cancer
  • whether the cancer is invasive or non-invasive
  • whether cancer is in the lymph nodes
  • whether the cancer has spread to other parts of the body beyond the breast

You also may see or hear certain words used to describe the stage of the breast cancer:

  • Local: The cancer is confined within the breast.
  • Regional: The lymph nodes, primarily those in the armpit, are involved.
  • Distant: The cancer is found in other parts of the body as well.

Stage 0
Stage 0 is used to describe non-invasive breast cancers, such as DCIS (ductal carcinoma in situ). In stage 0, there is no evidence of cancer cells or non-cancerous abnormal cells breaking out of the part of the breast in which they started, or getting through to or invading neighboring normal tissue.

Stage I

Stage I describes invasive breast cancer (cancer cells are breaking through to or invading normal surrounding breast tissue) in which the tumor measures up to 2 cm AND no lymph nodes are involved.

Microscopic invasion is possible in stage I breast cancer. In microscopic invasion, the cancer cells have just started to invade the tissue outside the lining of the duct or lobule, but the invading cancer cells can’t measure more than 1 mm.

Stage II
Stage II is divided into subcategories known as IIA and IIB.

Stage IIA describes invasive breast cancer in which:

no tumor can be found in the breast, but cancer cells are found in the lymph nodes under the arm (axillary) OR

the tumor measures 2 cm or smaller and has spread to the axillary lymph nodes OR

the tumor is larger than 2 cm but not larger than 5 cm and has not spread to the axillary lymph nodes

Stage IIB describes invasive breast cancer in which:

the tumor is larger than 2 cm but no larger than 5 cm and has spread to the axillary lymph nodes OR

the tumor is larger than 5 cm but has not spread to the axillary lymph nodes

Stage III
Stage III is divided into subcategories known as IIIA, IIIB, and IIIC.

Stage IIIA describes invasive breast cancer in which either:

no tumor is found, but cancer is found in axillary lymph nodes, which are clumped together or sticking to other structures, or cancer may have spread to lymph nodes near the breastbone OR

the cancer is any size and has spread to axillary lymph nodes, which are clumped together or sticking to other structures

Stage IIIB describes invasive breast cancer in which:

  • the cancer may be any size and has spread to the chest wall and/or skin of the breast AND
  • may have spread to axillary lymph nodes, which are clumped together or sticking to other structures, or cancer may have spread to lymph nodes near the breastbone

Inflammatory breast cancer is considered at least stage IIIB. Typical features of inflammatory breast cancer include:

  • reddening of a large portion of the breast skin
  • the breast feels warm and may be swollen
  • cancer cells have spread to the lymph nodes and may be found in the skin

Stage IIIC describes invasive breast cancer in which:

  • there may be no sign of cancer in the breast or, if there is a tumor, it may be any size and may have spread to the chest wall and/or the skin of the breast AND
  • the cancer has spread to lymph nodes above or below the collarbone AND
  • the cancer may have spread to axillary lymph nodes or to lymph nodes near the breastbone

Stage IV
Stage IV describes invasive breast cancer that has spread beyond the breast and nearby lymph nodes to other organs of the body, such as the lungs, distant lymph nodes, skin, bones, liver, or brain.

You may hear the words “advanced” and “metastatic” used to describe stage IV breast cancer. Cancer may be stage IV at first diagnosis or it can be a recurrence of a previous breast cancer that has spread to other parts of the body.