Once a person is diagnosed with cancer, his or her physician will try to determine how far the illness has progressed, including whether or not it has spread to other areas of the body. This effort is known as “staging.” Each cancer has its unique staging characteristics, and breast cancer is no different.
The stage of the cancer ultimately refers to how much cancer is present in the body, indicates the American Cancer Society. Doctors treating breast cancer adhere to the TNM staging system, which is overseen by the American Joint Committee on Cancer. This staging uses both clinical and pathological (surgical) systems for breast cancer staging. Pathological staging may be more accurate because it examines tissues taken during surgery or a biopsy.
T categories
T in the staging system refers to the tumor’s size and whether it has spread to the skin or chest wall under the breast. Higher numbers refer to larger tumors and greater spread.
TX: A primary tumor cannot be assessed.
T0: No evidence of primary tumor.
T1: Tumor is 2 centimeters (cm) or less across.
T2: Tumor is more than 2 cm but not more than 5 cm across.
T3: Tumor is more than 5 cm across.
T4: Tumor is of any size growing into the chest wall or skin.
N categories
N in the staging system identifies if the cancer has spread to the lymph nodes near the breast, and if so, how many.
NX: Nearby lymph nodes cannot be assessed, which can happen if they were previously removed.
N0: Cancer has not spread to nearby lymph nodes.
N1: Cancer has spread to one to three axillary (underarm) lymph node(s), and/or cancer is found in internal mammary lymph nodes (those near the breast bone) on a sentinel lymph node biopsy.
N2: Cancer has spread to four to nine lymph nodes under the arm. One or more area of cancer spread is larger than 2 millimeters (mm).
N3: Cancer has spread to any of the following: 10 or more axillary lymph nodes with area of cancer spread greater than 2 mm; to lymph nodes under the collarbone, with at least one area of cancer spread greater than 2 mm; cancer found in at least one axillary lymph node (with at least one area of cancer spread greater than 2 mm) and has enlarged the internal mammary lymph nodes; cancer in four or more axillary lymph nodes (with at least one area of cancer spread greater than 2 mm), and to the internal mammary lymph nodes on a sentinel lymph node biopsy; to the lymph nodes above the collarbone on the same side of the cancer with at least one area of cancer spread greater than 2 mm.
M categories
M indicates if the cancer has spread to distant organs.
M0: No distant spread is present on X-rays or other imaging and physical tests.
M1: Cancer has spread to other organs, notably the brain, bones, liver or lungs as determined by a biopsy or testing.
Note that this staging system also uses sub-stages within each category, which further breaks down breast cancer staging into more characteristics and combinations. The ACS says there are so many possibilities that can go into staging that two women at the same breast cancer stage may have different experiences.
Any sign of an abnormality in the breast or body merits a consultation with a doctor, who can determine if breast cancer is present. Lower numbers on TNM staging are desired, and can be achieved by catching breast cancer early.
