The TNM staging system (officially known as the TNM classification system of malignant tumours) is a cancer staging system overseen and published by the Union for International Cancer Control (UICC). The American Joint Committee on Cancer (AJCC) publishes the AJCC Cancer Staging Manual which is based upon - and for the most part identical to - the TNM system.
The TNM system has been widely adopted for the cancers of many body systems as a replacement for idiosyncratic disease-specific classification systems. It is currently in its eighth edition, published in October 2016 1,2.
In general the TNM system is not used for paediatric cancers.
TNM systematically describes the extent of malignancies - primarily on their anatomy - and categorises each malignancy by the status of the primary tumour (T), nodal involvement (N) and metastatic disease (M).
T, N, and M, are called categories, however the term stage is reserved for a grouping of TNM designations that have a similar prognosis.
Stages are numbered I through IV. Although often heard, it is incorrect to talk about the T or N or M stage of a tumour.
TNM staging system
The precise details depend on the primary tumour site and/or histology but in general:
- TX: primary tumour cannot be assessed
- T0: no evidence of primary tumour
- Tis: carcinoma in situ
- T1: site/tumour specific, generally small
- T2: site/tumour specific
- T3: site/tumour specific, generally large
- T4: site/tumour specific, generally direct extension into adjacent organs/tissues
- NX: nodes cannot be assessed
- N0: no regional nodal metastasis
- N1: site/tumour specific
- N2: site/tumour specific
- N3: site/tumour specific
When tumours involve non-regional nodes, the M category is usually applied
- M0: no distant metastasis
- M1: distant metastasis present
NB: No MX category exists, it was removed in the 6th edition, if presence of metastases is not known the cancer is assigned M0 2
The TNM system has been expanded to include other measures:
- R: resection status
- V: vascular invasion
Additional prefixes can be appended to define the TNM stage:
- c: clinical assessment data (e.g. cT1b)
- p: pathological data
- y: clinical (yc) or pathological (yp) data following systemic or radiation therapy be it prior to surgery or as a primary treatment
- r: clinical or pathological staging at the time of retreatment or recurrence for disease progression
a: for cancers discovered at autopsy (e.g. aT1)
- not for cancers known about or suspected prior to death
- m: multiple primary tumours of the same histology in the same organ, e.g. T2(m) or T2(5), the latter meaning that there are five primary tumours
Whereas T, N, and M, are called categories, the stage refers to a grouping of TNM designations that have similar prognosis. Stages are numbered I through IV. In general, M1 disease indicates stage IV. Stage 0 is assigned to carcinoma in situ. Stages are further broken down into subgroups, indicated by capital letters A, B and C which follow after the stage number (e.g. Stage 2B). Subgrouping is defined for each cancer site and provides additional prognostic information.
History and etymology
The TNM idea, as we know it, was developed by the French surgeon Pierre Denoix and colleagues in the 1940s, culminating in a groundbreaking publication in 1952 3,4. Professor Denoix was Director of the Institut Gustave Roussy, the first health facility in Europe dedicated to cancer research and care.
- 1. Mary K. Gospodarowicz, James D. Brierley, Christian Wittekind. TNM Classification of Malignant Tumours. (2017) ISBN: 9781119263579
- 2. Amin MB, Greene FL, Edge SB, Compton CC, Gershenwald JE, Brookland RK, Meyer L, Gress DM, Byrd DR, Winchester DP. The Eighth Edition AJCC Cancer Staging Manual: Continuing to build a bridge from a population-based to a more "personalized" approach to cancer staging. (2017) CA: a cancer journal for clinicians. 67 (2): 93-99. doi:10.3322/caac.21388 - Pubmed
- 3. Sobin LH. TNM: evolution and relation to other prognostic factors. (2003) Seminars in surgical oncology. 21 (1): 3-7. doi:10.1002/ssu.10014 - Pubmed
- 4. Asare EA, Grubbs EG, Gershenwald JE, Greene FL, Aloia TA. Setting the "stage" for Surgical Oncology fellows: Pierre Denoix and TNM staging. (2019) Journal of surgical oncology. doi:10.1002/jso.25404 - Pubmed
- 5. Doll R. The Pierre Denoix Memorial Lecture: nature and nurture in the control of cancer. (1999) European journal of cancer (Oxford, England : 1990). 35 (1): 16-23. Pubmed