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Staging is a way of describing where the cancer is located, how much the cancer has grown, and if or where it has spread. Doctors use diagnostic tests to determine the cancer's stage, so staging may not be complete until all the tests are finished. Knowing the stage helps the doctor to decide what kind of treatment is best and can help predict a patient's prognosis (chance of recovery). There are different stage descriptions for different types of cancer.
The most commonly used tool that doctors use to describe tumor stage is the TNM system. This system judges three factors: the size of the tumor itself, the presence of cancer in the lymph nodes where the cancer cells often first travel, and whether the tumor has spread to other parts of the body. The results are combined to determine the stage of cancer for each person. In breast cancer, there are five stages: stage 0 (zero), which is noninvasive ductal carcinoma in situ (DCIS), and stages I through IV (one through four), which are used for invasive breast cancer. Stage provides a common way of describing the cancer so doctors can work together with the patient to plan the best treatments.
TNM is an abbreviation for tumor (T), node (N), and metastasis (M). Doctors look at these three factors to determine the stage of cancer:
- How large is the primary tumor and where is it located? (Tumor, T)
- Has the tumor spread to the lymph nodes? (Node, N)
- Has the cancer metastasized to other parts of the body? (Metastasis, M)
There are two types of TNM staging for breast cancer. First, the clinical stage is based on the results of tests done before surgery, such as a physical examination, x-rays, CT scans, and MRI tests. Then, the pathologic stage is assigned based on information found during surgery plus the laboratory results (pathology) of the breast tissue and any lymph nodes removed during surgery. It is usually determined several days after surgery when the results from testing the tumor and lymph nodes are ready. In general, more importance is placed on the pathologic stage than the clinical stage.
Tumor. Using the TNM system, the “T” plus a letter or number (0 to 4) is used to describe the size and location of the tumor. Some stages are divided into smaller groups that help describe the tumor in even more detail.
TX: The primary tumor cannot be evaluated.
T0: There is no evidence of cancer in the breast.
Tis: Refers to carcinoma (cancer) in situ. The cancer is confined within the ducts or lobules of the breast tissue and has not spread into the surrounding tissue of the breast. There are three types of breast carcinoma in situ:
Tis (DCIS): DCIS is a noninvasive cancer, but if not removed it can later develop into an invasive breast cancer. DCIS means that cancer cells have been found in breast ducts and have not spread past the layer of tissue where they began.
Tis (LCIS): Lobular carcinoma in situ (LCIS) describes abnormal cells found in the lobules or glands of the breast. LCIS is not cancer, but it increases the risk of developing invasive breast cancer.
Tis (Paget’s): Paget’s disease of the nipple is a rare form of early, noninvasive cancer that is only in the skin cells of the nipple. Sometimes Paget’s disease is associated with another invasive breast cancer. If there is also an invasive breast cancer present, it is classified according to the stage of the invasive tumor.
T1: The invasive part of the tumor in the breast is 20 millimeters (mm) or smaller in size at its widest area (a little less than an inch). This stage is then broken into three substages depending on the size of the tumor, called T1a (tumor is larger than 1 mm, but 5mm or smaller), T1b (tumor is larger than 5 mm, but 10 mm or smaller), and T1c (tumor is larger than 10 mm, but 20 mm or smaller).
T2: The invasive part of the tumor is larger than 20 mm but not larger than 50 mm.
T3: The invasive part of the tumor is larger than 50 mm.
T4: The tumor has grown into the chest wall (called T4a) and/or to the skin (called T4b). If there are signs of both, it is called T4c, and inflammatory breast cancer is called T4d.
Node. The “N” in the TNM staging system stands for lymph nodes. Lymph nodes located under the arm, above and below the collarbone, and under the breastbone are called regional lymph nodes. Lymph nodes in other parts of the body are called distant lymph nodes. As explained above, if the doctor evaluates the lymph nodes before surgery, based on other tests and/or a physical examination, a letter “c” (for “clinical” staging) is placed in front of the “N.” If the doctor evaluates the lymph nodes after surgery, which is a more accurate assessment, a letter “p” (for “pathologic” staging) is placed in front of the “N.” The information below describes the pathologic staging.
NX: The lymph nodes cannot be evaluated.
N0: No cancer was found in the lymph nodes.
N0(i+): When very small areas of “isolated” tumor cells are found in a lymph node (less than 0.2 mm or less than 200 cells), the nodes are still called N0, but an “i+” is also listed.
N1mic: Cancer in the lymph nodes is larger than 0.2 mm but less than 2 mm in size (microscopic).
N1: The cancer has spread to one to three axillary lymph nodes under the arm. This category can include positive internal mammary lymph nodes (found under the sternum or breastbone) if found during a sentinel lymph node procedure and not otherwise clinically detected.
N2: The cancer has spread to four to nine lymph nodes under the arm (called N2a), or to clinically apparent internal mammary lymph nodes (lymph nodes under the sternum on the inside of the chest, called N2b) without spread to the axillary nodes.
N3: The cancer has spread to 10 or more lymph nodes under the arm or to the infraclavicular lymph nodes (located under the clavicle, or collarbone); this is called N3a. Or, the cancer has spread to the internal mammary nodes with axillary node involvement (N3b) or to the supraclavicular (located above the clavicle) lymph nodes (N3c).
If there is cancer in the lymph nodes, knowing how many lymph nodes are involved, and where they are helps doctors to plan treatment. The pathologist can find out the number of axillary lymph nodes that contain cancer after they are removed during surgery. It is not common to remove the supraclavicular or internal mammary lymph nodes during surgery. If there is cancer in these lymph nodes, treatment other than surgery, such as radiation therapy, chemotherapy, and hormonal therapy is used to control the disease.
Distant metastasis. The “M” in the TNM system indicates whether the cancer has spread to other parts of the body.
MX: Distant spread cannot be evaluated.
M0: The disease has not metastasized.
M0 (i+): There is no clinical or radiographic evidence of distant metastases, but microscopic evidence of tumor cells is found in the blood, bone marrow, or other lymph nodes that are no larger than 0.2 mm in a patient without other evidence of metastases.
M1: There is evidence of metastasis to another part of the body (breast cancer cells growing in other organs).
Cancer stage grouping
Doctors assign the stage of the cancer by combining the T, N, and M classifications.
Stage 0: Stage zero (0) describes disease that is only in the ducts and lobules of the breast tissue and has not spread to the surrounding tissue of the breast. It is also called noninvasive cancer (Tis, N0, M0).
Stage IA: The tumor is small, invasive, and has not spread to the lymph nodes (T1, N0, M0).
Stage IB: Cancer has spread only to the lymph nodes, where it is larger than 0.2 mm but less than 2 mm in size. There is either no evidence of a tumor in the breast or the tumor in the breast is 20 mm or smaller (T0 or T1, N1mic, M0).
Stage IIA: Any one of these conditions:
- There is no evidence of a tumor in the breast, but the cancer has spread to the axillary lymph nodes but not to distant parts of the body. (T0, N1, M0).
- The tumor is 20 mm or smaller and has spread to the axillary lymph nodes (T1, N1, M0).
- The tumor is larger than 20 mm but not larger than 50 mm and has not spread to the axillary lymph nodes (T2, N0, M0).
Stage IIB: Either of these conditions:
- The tumor is larger than 20 mm but not larger than 50 mm and has spread to one to three axillary lymph nodes (T2, N1, M0).
- The tumor is larger than 50 mm but has not spread to the axillary lymph nodes (T3, N0, M0).
Stage IIIA: The cancer of any size has spread to four to nine axillary lymph nodes, but not to other parts of the body (T0, T1, T2 or T3, N2, M0). Stage IIIA may also be a tumor larger than 50 mm that has spread to one to three lymph nodes (T3, N1, M0).
Stage IIIB: The tumor has spread to the chest wall or caused swelling or ulceration of the breast or is diagnosed as inflammatory breast cancer. It may or may not have spread to the lymph nodes under the arm, but it has not spread to other parts of the body (T4; N0, N1 or N2; M0).
Stage IIIC: A tumor of any size that has not spread to distant parts of the body but has spread to 10 or more axillary lymph nodes or the lymph nodes in the N3 group (any T, N3, M0).
Stage IV (metastatic): The tumor can be any size and has spread to another organ (bones, lungs, brain, liver, distant lymph nodes, or chest wall (any T, any N, M1). Metastatic cancer spread is found when the cancer is first diagnosed about 5% to 6% of the time. Most commonly, metastatic breast cancer is found after a previous diagnosis of early-stage breast cancer.
Recurrent: Recurrent cancer is cancer that comes back after treatment, and can be either local or distant or both. If there is a recurrence, the cancer may need to be staged again (called re-staging) using the system above.
Used with permission of the American Joint Committee on Cancer (AJCC), Chicago, Illinois. The original source for this material is the AJCC Cancer Staging Manual Seventh Edition (2010) published by Springer-Verlag New York, www.cancerstaging.net.