This is a medical question of type : stages 
 What are the stages of Breast Cancer ? 
 Key Points
                    - After breast cancer has been diagnosed, tests are done to find out if cancer cells have spread within the breast or to other parts of the body.     - There are three ways that cancer spreads in the body.    - Cancer may spread from where it began to other parts of the body.    - The following stages are used for breast cancer:         - Stage 0 (carcinoma in situ)     - Stage I     - Stage II     - Stage IIIA     - Stage IIIB     - Stage IIIC     - Stage IV
                
                
                    After breast cancer has been diagnosed, tests are done to find out if cancer cells have spread within the breast or to other parts of the body.
                    The process used to find out if 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.   Some procedures may expose the unborn baby to harmful radiation or dyes. These procedures are done only if absolutely necessary. Certain actions can be taken to expose the unborn baby to as little radiation as possible, such as the use of a lead-lined shield to cover the abdomen.   The following tests and procedures may be used to stage breast cancer during pregnancy:         -   Sentinel lymph node biopsy : The removal of the sentinel lymph node during surgery. The sentinel lymph node is the first lymph node to receive lymphatic drainage from a tumor. It is the first lymph node the cancer is likely to spread to from the tumor. A radioactive substance and/or blue dye is injected near the tumor. The substance or dye flows through the lymph ducts to the lymph nodes. The first lymph node to receive the substance or dye is removed. A pathologist views the tissue under a microscope to look for cancer cells. If cancer cells are not found, it may not be necessary to remove more lymph nodes.     -   CT scan (CAT scan): A procedure that makes a series of detailed pictures of areas inside the body, taken from different angles. The pictures are made by a computer linked to an x-ray machine. This procedure is also called computed tomography, computerized tomography, or computerized axial tomography.     -   Bone scan : A procedure to check if there are rapidly dividing cells, such as cancer cells, in the bone. A very small amount of radioactive material is injected into a vein and travels through the bloodstream. The radioactive material collects in bones with cancer and is detected by a scanner.    -   PET scan (positron emission tomography scan): A procedure to find malignant tumor cells in the body. A small amount of radioactive glucose (sugar) is injected into a vein. The PET scanner rotates around the body and makes a picture of where glucose is being used in the body. Malignant tumor cells show up brighter in the picture because they are more active and take up more glucose than normal cells do.     -    MRI (magnetic resonance imaging): A procedure that uses a magnet, radio waves, and a computer to make a series of detailed pictures of areas inside the body, such as the brain. This procedure is also called nuclear magnetic resonance imaging (NMRI).    -   Ultrasound exam: A procedure in which high-energy sound waves (ultrasound) are bounced off internal tissues or organs, such as the liver, and make echoes. The echoes form a picture of body tissues called a sonogram. The picture can be printed to be looked at later.    -   Chest x-ray : An x-ray of the organs and bones inside the chest. An x-ray is a type of energy beam that can go through the body and onto film, making a picture of areas inside the body.
                
                
                    There are three ways that cancer spreads in the body.
                    Cancer can spread through tissue, the lymph system, and the blood:         - Tissue. The cancer spreads from where it began by growing into nearby areas.     - Lymph system. The cancer spreads from where it began by getting into the lymph system. The cancer travels through the lymph vessels to other parts of the body.     - Blood. The cancer spreads from where it began by getting into the blood. The cancer travels through the blood vessels to other parts of the body.
                
                
                    Cancer may spread from where it began to other parts of the body.
                    When cancer spreads to another part of the body, it is called metastasis. Cancer cells break away from where they began (the primary tumor) and travel through the lymph system or blood.         - Lymph system. The cancer gets into the lymph system, travels through the lymph vessels, and forms a tumor (metastatic tumor) in another part of the body.    - Blood. The cancer gets into the blood, travels through the blood vessels, and forms a tumor (metastatic tumor) in another part of the body.        The metastatic tumor is the same type of cancer as the primary tumor. For example, if breast cancer spreads to the bone, the cancer cells in the bone are actually breast cancer cells. The disease is metastatic breast cancer, not bone cancer.
                
                
                    The following stages are used for breast cancer:
                    This section describes the stages of breast cancer. The breast cancer stage is based on the results of testing that is done on the tumor and lymph nodes removed during surgery and other tests.     Stage 0 (carcinoma in situ)    There are 3 types of breast carcinoma in situ:            -  Ductal carcinoma in situ (DCIS) is a noninvasive condition in which abnormal cells are found in the lining of a breast duct. The abnormal cells have not spread outside the duct to other tissues in the breast. In some cases, DCIS may become invasive cancer and spread to other tissues. At this time, there is no way to know which lesions could become invasive.     -  Lobular carcinoma in situ (LCIS) is a condition in which abnormal cells are found in the lobules of the breast. This condition seldom becomes invasive cancer. However, having LCIS in one breast increases the risk of developing breast cancer in either breast.     -  Paget disease of the nipple is a condition in which abnormal cells are found in the nipple only.               Stage I     In stage I, cancer has formed. Stage I is divided into stages IA and IB.            - In stage IA, the tumor is 2 centimeters or smaller. Cancer has not spread outside the breast.     - In stage IB, small clusters of breast cancer cells (larger than 0.2 millimeter but not larger than 2 millimeters) are found in the lymph nodes and either:                  - no tumor is found in the breast; or       - the tumor is 2 centimeters or smaller.                         Stage II     Stage II is divided into stages IIA and IIB.            - In stage IIA:                  - no tumor is found in the breast or the tumor is 2 centimeters or smaller. Cancer (larger than 2 millimeters) is found in 1 to 3 axillary lymph nodes or in the lymph nodes near the breastbone (found during a sentinel lymph node biopsy); or        - the tumor is larger than 2 centimeters but not larger than 5 centimeters. Cancer has not spread to the lymph nodes.                - In stage IIB, the tumor is:                  - larger than 2 centimeters but not larger than 5 centimeters. Small clusters of breast cancer cells (larger than 0.2 millimeter but not larger than 2 millimeters) are found in the lymph nodes; or        - larger than 2 centimeters but not larger than 5 centimeters. Cancer has spread to 1 to 3 axillary lymph nodes or to the lymph nodes near the breastbone (found during a sentinel lymph node biopsy); or        - larger than 5 centimeters. Cancer has not spread to the lymph nodes.                          Stage IIIA     In stage IIIA:            - no tumor is found in the breast or the tumor may be any size. Cancer is found in 4 to 9 axillary lymph nodes or in the lymph nodes near the breastbone (found during imaging tests or a physical exam); or      - the tumor is larger than 5 centimeters. Small clusters of breast cancer cells (larger than 0.2 millimeter but not larger than 2 millimeters) are found in the lymph nodes; or      - the tumor is larger than 5 centimeters. Cancer has spread to 1 to 3 axillary lymph nodes or to the lymph nodes near the breastbone (found during a sentinel lymph node biopsy).               Stage IIIB     In stage IIIB, the tumor may be any size and cancer has spread to the chest wall and/or to the skin of the breast and caused swelling or an ulcer. Also, cancer may have spread to:            - up to 9 axillary lymph nodes; or     - the lymph nodes near the breastbone.           Cancer that has spread to the skin of the breast may also be inflammatory breast cancer. See the section on Inflammatory Breast Cancer for more information.       Stage IIIC     In stage IIIC, no tumor is found in the breast or the tumor may be any size. Cancer may have spread to the skin of the breast and caused swelling or an ulcer and/or has spread to the chest wall. Also, cancer has spread to:             - 10 or more axillary lymph nodes; or     -  lymph nodes above or below the collarbone; or     - axillary lymph nodes and lymph nodes near the breastbone.           Cancer that has spread to the skin of the breast may also be inflammatory breast cancer. See the section on Inflammatory Breast Cancer for more information.    For treatment, stage IIIC breast cancer is divided into operable and inoperable stage IIIC.        Stage IV     In stage IV, cancer has spread to other organs of the body, most often the bones, lungs, liver, or brain.