TNM staging

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The TNM staging system (officially known as the TNM classification system of malignant tumors) 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 .

In general the TNM system is not used for pediatric cancers.

TNM systematically describes the extent of malignancies - primarily on their anatomy - and categorizes each malignancy by the status of the primary tumor (T), nodal involvement (N) and metastatic disease (M).

Terminology

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 tumor.

TNM staging system

The precise details depend on the primary tumor site and/or histology but in general:

T: Tumor

TX: primary tumor cannot be assessed
T0: no evidence of primary tumor
Tis: carcinoma in situ
T1: site/tumor specific, generally small
T2: site/tumor specific
T3: site/tumor specific, generally large
T4: site/tumor specific, generally direct extension into adjacent organs/tissues

N: Nodes

NX: nodes cannot be assessed
N0: no regional nodal metastasis
N1: site/tumor specific
N2: site/tumor specific
N3: site/tumor specific

When tumors involve non-regional nodes, the M category is usually applied

M: Metastases

M0: no distant metastasis
M1: distant metastasis present

NB: No MX category exists, it was removed in the 6 edition, if presence of metastases is not known the cancer is assigned M0

Other descriptors

The TNM system has been expanded to include other measures:

R: resection status
V: vascular invasion

Prefixes

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

Suffix

m: multiple primary tumors of the same histology in the same organ, e.g. T2(m) or T2(5), the latter meaning that there are five primary tumors

Stage

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 . Professor Denoix was Director of the Institut Gustave Roussy, the first health facility in Europe dedicated to cancer research and care.