TNM

Overview
TNM Classification of Malignant Tumours (TNM) is the cancer staging system developed and maintained by the International Union Against Cancer (UICC) to achieve consensus on one globally recognised standard for classifying the extent of spread of cancer. The TNM classification is also used by the American Joint Committee on Cancer (AJCC) and the International Federation of Gynecology and Obstetrics (FIGO). In 1987, the UICC and AJCC staging systems were unified into a single staging system.

Broad outline
Each tumor has its own TNM classification. Not all tumors have TNM classifications, but most do. For instance, there is no TNM classification for brain tumors.

The general outline for the TNM classification is below. The values given in parenthesis give a range of what can be used for all cancer types, but not all cancers use this full range.

Mandatory parameters ('T', 'N', and 'M')

 * T (a,is,(0),1-4): size or direct extent of the primary tumour
 * N (0-3): spread to regional lymph nodes
 * M (0/1): distant metastasis

Use of an "X" instead of a number or other suffix means that the parameter was not assessed.

Other parameters

 * G (1-4): the grade of the cancer cells (i.e. they are "low grade" if they appear similar to normal cells, and "high grade" if they appear poorly differentiated)
 * R (0/1/2): the completeness of the operation (resection-boundaries free of cancer cells or not)
 * L (0/1): invasion into lymphatic vessels
 * V (0/1): invasion into vein
 * C (1-4): a modifier of the certainty (quality) of the last mentioned parameter

Prefix modifiers

 * c: stage given by clinical examination of a patient. The c-prefix is implicit in absence of the p-prefix
 * p: stage given by pathologic examination of a surgical specimen
 * y: stage assessed after neoadjuvant therapy

For the T, N and M parameters exist subclassifications for some cancer-types (e.g. T1a, Tis, N1i)

Examples
Most Stage I tumors are curable; most Stage IV tumors are inoperable.
 * Small, low grade cancer, no metastasis, no spread to regional lymph nodes, cancer completely removed, resection material seen by pathologist - pT1 pN0 M0 R0 G1; this grouping of T, N, and M would be considered Stage I
 * Large, high grade cancer, with spread to regional lymph nodes and other organs, not completely removed, seen by pathologist - pT4 pN2 M1 R1 G3; this grouping of T, N, and M would be considered Stage IV
 * N0 tumor cells absent from regional lymph nodes
 * N1 tumor cells spread to closest or small number of regional lymph nodes
 * N3 tumor cells spread to most distant or numerous regional lymph nodes
 * M0 no distant metastasis
 * M1 metastasis to distant organs (beyond regional lymph nodes)

Uses and aims
Some of the aims for adopting a global standard are to:
 * Aid medical staff in staging the tumour helping to plan the treatment.
 * Give an indication of prognosis.
 * Assist in the evaluation of the results of treatment.
 * Enable facilities around the world to collate information more productively.

Since the number of combinations of categories is high, combinations are grouped to stages for better analysis.

Versions
The current version of TNM is TNM6, released in 2002. However, some still prefer TNM5, and recommend its continued use.