The TNM classification system describes the extent of many types of solid tumour cancers. It gives doctors a common language to describe a cancer. The Union for International Cancer Control (UICC) and the American Joint Committee on Cancer (AJCC) both use the TNM classification system to describe the extent of many solid tumour cancers.
TNM is based on 3 components:
indicates the size of the primaryprimaryThe site or area in the body where cancer started. tumour and the degree of spread into nearby tissues (local invasion)
indicates whether or not the cancer has spread to nearby lymph nodes, the size of the nodes that contain cancer and how many lymph nodes contain cancer
indicates whether or not cancer has spread (metastasized) to distant organs
Additional letters or numbers are placed after T, N and M to provide more specific details:
Primary tumour (T)
primary tumour cannot be assessed
no evidence of primary tumour
carcinoma in situcarcinoma in situA very early stage of cancer in which tumour cells have not yet invaded surrounding tissues.
T1, T2, T3 or T4
The number corresponds to the size of the primary tumour and how far it has spread. The higher the number, the larger the tumour and the greater the spread to nearby structures and tissue.
Regional lymph nodes (N)
regional lymph nodes cannot be assessed
no evidence that regional lymph nodes are involved
N1, N2 or N3
the number corresponds to the degree of spread of cancer to the regional lymph nodes
Note: If the primary tumour extends into nearby lymph nodes (regional lymph nodes), it is considered a lymph node metastasis. Metastasis in any other group of lymph nodes is usually considered distant metastasis.
Distant metastasis (M)
no evidence of distant metastasis
distant metastasis is present
The TNM staging system varies from one type of cancer to another.
Solid tumours are usually given both clinical and pathological TNM classifications.
The pathological classification is more accurate in assessing tumour size and spread to the lymph nodes than the clinical classification. However, the pathological classification often cannot take into consideration other variables like distant metastasis. To arrive at the most accurate staging, both pathological and clinical staging have to be taken into consideration.