The process used to find out whether the cancer has spread within the breast or to other parts of the body is called staging. The information gathered from the staging process determines the stage of the disease. It is important to know the stage in order to plan treatment.

The following stages are descriptive for breast cancer:

Stage 0 (carcinoma in situ)

There are two types of breast carcinoma in situ: 

• Ductal carcinoma in situ (DCIS) is a noninvasive, precancerous condition in which abnormal cells are found in the lining of a breast duct. 
• Lobular carcinoma in situ (LCIS) is a condition in which abnormal cells are found in the lobules (milk producing tissue) of the breast.

Stage I

The tumor is 2 centimeters or smaller and has not spread outside the breast.

Stage IIA

• No tumor is found in the breast, but cancer is found in the axillary lymph nodes; or 
• The tumor is 2 centimeters or smaller and has spread to the axillary lymph nodes; or 
• The tumor is between 2 and 5 centimeters but has not spread to the axillary lymph nodes.

In Stage IIB

The tumor is either: 

• Between 2 and 5 centimeters and has spread to the axillary lymph nodes; or
• Larger than 5 centimeters but has not spread to the axillary lymph nodes.

In Stage IIIA

• No tumor is found in the breast, but cancer is found in axillary lymph nodes that are attached to each other or to other structures; or
• The tumor is 5 centimeters or smaller and has spread to axillary lymph nodes that are attached to each other or to other structures; or 
• The tumor is larger than 5 centimeters and has spread to axillary lymph nodes that may or may not be attached to each other or to other structures.

In Stage IIIB

The cancer may be any size and:

• Has spread to tissues near the breast (the skin or chest wall, including the ribs and muscles in the chest); and 
• May have spread to lymph nodes within the breast or under the arm.

In Stage IIIC,

In Stage IIIC, the cancer: 

• Has spread to lymph nodes beneath the collarbone and near the neck; and
• May have spread to lymph nodes within the breast or under the ar and to tissues near the breast.
• Stage IIIC breast cancer is divided into operable and inoperable stage IIIC.

In operable Stage IIIC, the cancer:

• Is found in 10 or more of the lymph nodes under the arm; or 
• Is found in the lymph nodes beneath the collarbone and near the neck on the same side of the body as the breast with cancer; or
• Is found in lymph nodes within the breast itself and in lymph nodes under the arm.

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

Stage IV

The cancer has spread to other organs of the body, most often the bones, lungs, liver, or brain. 

Recurrent

Breast cancer is cancer that has recurred (come back) after it has been treated. The cancer may come back in the same breast, the other breast, or in other parts of the body.