‘TNM’ stands for Tumour, Node, Metastasis. 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. This system can describe the size of a primary tumour, whether there are lymph nodes with cancer cells in them and whether the cancer has spread to a different part of the body.
In the 1980s, Chahinian added detailed tumor stages to the Butchart System, such as lymph node stages and metastases stages. This staging system was referred to as the TNM staging system. In 1990 the International Union Against Cancer (UICC) expounded on Chahinian’s mesothelioma stages and proposed a revitalized version of the TNM standard which took into consideration emerging information about the impact of T and N status on survival, providing more accurate anatomic descriptions of involvement of the primary tumor. In 1995, these modifications were proposed by the International Mesothelioma Interest Group (IMIG) to the medical community. The resulting staging system, which was developed to provide the basic framework for appropriate analysis of probable clinical trials involving new treatment protocols, was adopted by the American Joint Committee on Cancer (AJCC) and the International Union Against Cancer (UICC) in 2002 for their TNM staging system. According to the American Cancer Society website, most medical facilities use the TNM system as their main method for cancer reporting.
Members involved in clinical research in malignant pleural mesothelioma developed this system to address the lack of an accurate universally accepted staging system. Members of the IMIG include clinial researchers from around the world as well as the originators of previously proposed staging systems. The new staging system is based on the analysis of emerging information about the impact of T and N status on survival.
The difference between the TNM system and previous taging systems is that the T descriptors designated as T1, T2, T3, and T4, provide more precise anatomic definitions of the local extent of the primary tumor. The N descriptors, designated as N0, N1, N2, and N3, are virtually identical to those used in the International Lung Cancer Staging System. The stage groupings recognize new data about the better prognosis of T1 and N0 tumors and classify those tumors into stages I and II.
Below is a description provided by the National Cancer Institute, http://www.cancer.gov/.
Primary Tumor (T)
TX
Primary tumor cannot be evaluated
T0
No evidence of primary tumor
T1, T2, T3, T4
Size and/or extent of the primary tumor
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)
StageDefinition
Stage 0
Carcinoma in situ (early cancer that is present only in the layer of cells in which it began).
Stage I, Stage II, and Stage III
Higher numbers indicate more extensive disease: greater tumor size, and/or spread of the cancer to nearby lymph nodes and/or organs adjacent to the primary tumor.
Stage IV
The cancer has spread to another organ.
‘T’ can be 1 to 4, with ’1′ being a small tumour and ’4′ a large one
‘N’ can be 0 to 3, with ’0′ meaning no positive lymph nodes and ’3′ many positive nodes ‘M’ is either 0 or 1, with ’0′ meaning the cancer has not spread and ’1′ meaning that it has spread
Number Systems: These usually have a scale of 1 to 4 (or sometimes A to D). ’1′ typically means a small tumour that has not spread and no positive lymph nodes. ’4′ would mean that the cancer had spread to other major organs in the body.
Sometimes the letters A, B or C are used to further divide the number categories – for example, stage 3C cervical cancer. P can be used before the letters TNM to mean a tumour that has been removed by surgery.
