The TNM system is one of the most commonly used staging systems. This system has been accepted by the International Union Against Cancer (UICC) and the American Joint Committee on Cancer (AJCC). Most medical facilities use the TNM system as their main method for cancer reporting.
The TNM system is based on the extent of the tumor (T), the extent of spread to the lymph nodes (N), and the presence of metastasis (M). A number is added to each letter to indicate the size or extent of the tumor and the extent of spread.
Primary Tumor (T)
TX Primary tumor cannot be evaluated
T0 No evidence of primary tumor
Tis Carcinoma in situ
T1, T2, T3, T4 Size and/or extent of the primary tumor
Regional Lymph Nodes (N)
NX Regional lymph nodes cannot be evaluated
N0 No regional lymph node involvement (no cancer found in the lymph nodes)
N1, N2, N3 Involvement of regional lymph nodes (number and/or extent of spread)
Distant Metastasis (M)
MX Distant metastasis cannot be evaluated
M0 No distant metastasis (cancer has not spread to other parts of the body)
M1 Distant metastasis (cancer has spread to distant parts of the body)
For example, breast cancer T3 N2 M0 refers to a large tumor that has spread outside the breast to nearby lymph nodes, but not to other parts of the body. Prostate cancer T2 N0 M0 means that the tumor is located only in the prostate and has not spread to the lymph nodes or any other part of the body.
For many cancers, TNM combinations correspond to one of five stages. Criteria for stages differ for different types of cancer. For example, bladder cancer T3 N0 M0 is stage III; however, colon cancer T3 N0 M0 is stage II.