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Once breast cancer is diagnosed, further tests are performed to determine if the cancer has spread. This process is known as breast cancer staging. The stage determines the appropriate treatment options.
Stage 0 describes non-invasive breast cancers. In this stage, there is no evidence of cancer cells or noncancerous abnormal cells beyond the site of origin. There are two types of stage 0, ductal carcinoma in situ and lobular carcinoma in situ.
Ductal carcinoma in situ (DCIS) is a noninvasive condition in which abnormal cells occur in the lining of a breast duct and have not spread to surrounding tissue.
DCIS may become invasive. Lobular carcinoma in situ (LCIS) is a condition in which abnormal cells are found in the lobules of the breast and seldom becomes invasive.
Stage 1 describes invasive breast cancers and is subdivided into stage 1A and stage 1B. A stage 1A tumor is 2 centimeters or smaller and has not spread outside of the breast.
Stage 1B describes a small cluster of cancer cells, which measure between 0.2 and 2 millimeters, that are found in the lymph nodes with no tumor in the breast. Stage 1B also describes a tumor, which is 2 centimeters or smaller and a small cluster of cancer cells, which measure between 0.2 and 2 millimeters, found in the lymph nodes.
Stage 2 is divided into stage 2A and stage 2B. Stage 2A describes cancer found in the lymph nodes under the arm but not in the breast; a tumor that is 2 centimeter or smaller and has spread to the axillary lymph nodes, which are located under the arm; or a tumor that is between 2 to 5 centimeters and has not spread to the axillary lymph nodes.
Stage 2B describes an invasive tumor that is either larger than 2 centimeters but less than 5 centimeters and has spread to the axillary lymph nodes; or an invasive tumor that is larger than 5 centimeters and has not spread to the axillary lymph nodes.
Stage 3 is divided into three subcategories.