'Staging' is a method that has been developed to describe the extent of cancer growth. Breast cancer is 'staged' by information that is obtained from surgical and other findings. Specifically, information is gathered from the pathology (disease) report that accompanies a lumpectomy (lump removal), mastectomy (breast removal), or other form of breast surgery. In addition, staging is based upon findings from imaging studies - such as chest x-ray, abdominal ultrasound (images produced by high-frequency sound waves) computed tomography (CT or CAT scan; computer-assisted technique that produces cross-sectional images of the body), and bone scans.
The physician uses all available findings to choose a stage that best describes the person's condition. Staging helps to predict how an individual will fare over time - that is, it helps the physician to estimate how long a person will live and the risk of cancer recurrence, or relapse. Correspondingly, staging allows the physician to customize cancer treatment. In general, the lower the stage, the better the person's prognosis (expected outcome).
The TNM System
Pathologists (disease specialists) use a specific system to stage breast cancer. This method- known as the TNM system - was devised by the American Joint Committee on Cancer (AJCC) in collaboration with the National Cancer Institute (NCI). Within the TNM system, "T" refers to tumor size, "N" refers to lymph node involvement, and "M" refers to the extent of metastasis. The primary tumor (T) is ranked within one of the following categories:
Tumor cannot be assessed
No evidence of primary tumor
Carcinoma in situ, or Paget's disease of the nipple, without a detectable tumor mass
Tumor two centimeters or less (< 2 cm) in greatest dimension
Tumor more than two centimeters (> 2 cm), but less than five centimeters (< 5 cm), in greatest dimension
Tumor more than five centimeters (> 5 cm) in greatest dimension
Tumor of any size, with direct spread to chest wall or skin (includes inflammatory carcinoma and ulceration of the breast skin)
The extent of lymph node (N) involvement is described by the following categories:
Regional lymph nodes are metastasis-free
Metastasis to movable, same-side, axillary (armpit) lymph node(s)
Metastasis to same-side lymph node(s) fixed to one another or to other structures
Metastasis to same-side lymph nodes beneath the breastbone (internal mammary nodes)
Metastasis (M) is specified by the categories:
The presence of distant metastasis cannot be assessed
No distant metastases are found
Distant metastases are present
To simplify this information, the TNM classifications are grouped within four basic stages, labeled stage 0 through stage IV (0-4).
in situ breast cancer - Tis, N0, M0
T1, N0, M0
T0-1, N1, M0, or T2, N0, M0
T2, N1, M0, or T3, N0, M0
T0-2, N2, M0, or T3, N1-2, M0
T4, N (any), M0, or T(any), N3, M0
T(any), N(any), M1
The lower the stage number, the less the cancer has grown and spread. For example, a "stage I" breast cancer is relatively small and has not yet spread to the lymph nodes or other sites. By contrast, a "stage IV" cancer is much more serious, as it has already metastasized to the lymph nodes as well as another location(s).
Women with low-stage tumors have a better chance of surviving breast cancer than women with high-stage tumors. Recent findings from the National Cancer Institute (NCI) indicate that 5-year survival rates are 96% for limited, low-stage breast cancers (stage 0, stage I, and some stage II cancers), 75% for breast cancers that have invaded the surrounding tissue (stage II & III cancers), and only 20% for breast cancers that have metastasized (stage IV cancers). Unfortunately, survival rates are lower and breast cancer stages tend to be higher among women from low socioeconomic backgrounds.