A scale of 0 to IV: Understanding the stages of breast cancer

Breast cancer is usually described as one of five stages, ranging from zero, which describes noninvasive cancers that remain within their original location, to stage four, invasive cancers that have spread outside the breast to other parts of the body.

The stage is determined by four characteristics: the size of the cancer, whether the cancer is invasive or noninvasive, whether cancer is in the lymph nodes and whether the cancer has spread to other parts of the body beyond the breast.

Here, descriptions of the five stages according to breastcancer.org:

Stage 0

Stage 0 is used to describe noninvasive breast cancers. In this stage, there is no evidence of cancer cells or noncancerous 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) Stage I is divided into subcategories known as IA and IB.

Stage IA describes invasive breast cancer in which:

> the tumor measures up to 2 centimeters AND

> the cancer has not spread outside the breast; no lymph nodes are involved

Stage IB describes invasive breast cancer in which:

> there is no tumor in the breast; instead, small groups of cancer cells -- larger than 0.2 millimeter but not larger than 2 millimeters -- are found in the lymph nodes, OR

> there is a tumor in the breast that is no larger than 2 centimeters, and there are small groups of cancer cells -- larger than 0.2 millimeter but not larger than 2 millimeters -- in the lymph nodes.

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 centimeters or smaller and has spread to the axillary lymph nodes OR

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

Stage IIB describes invasive breast cancer in which:

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

> the tumor is larger than 5 centimeters 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

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.