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The TNM Staging System 

The TNM Staging System

Chapter:
Nomenclature
Author(s):

Harriet S. Meyer

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The TNM Staging System

The TNM staging system1-9 is an internationally standardized system for the staging of cancer and is in its seventh decade of continuing formulation. The TNM classification is put forth by the American Joint Committee on Cancer (AJCC) and the International Union Against Cancer (UICC; http://www.uicc.org).1 The AJCC’s Cancer Staging Manual2 and the UICC’s TNM Classification of Malignant Tumours3 present the stages of cancer as defined by TNM classifications. The TNM definitions and stage groupings are based on prognostic outcome. Information about TNM may be accessed at the UICC website, http://www.uicc.org/index.php?id=508. The TNM symbols follow.

  • T: tumor (indicates size, extent, or depth of penetration of the primary tumor). T is followed by numerical or other suffixes set on the line, eg:

    TX: primary tumor cannot be assessed

    T0: no evidence of a primary tumor

    Tis: in situ carcinoma

    T1, T2, T3, T4: increasing size, extent, or other characteristics of the primary tumor

Note: The number following T does not refer to an absolute size. For example, for one type of tumor, T1 may indicate size of 2 cm or less, for another, a depth (or thickness) of 0.75 mm or less, and for another, tumor confinement within the underlying mucosa.

  • N: node (indicates the absence or presence and extent of regional lymph node involvement)

    NX: regional lymph nodes cannot be assessed

    N0: no regional lymph node metastasis

    N1, N2, N3: increasing metastatic involvement of regional lymph nodes according to criteria that vary for different anatomic sites

  • M: metastasis (indicates absence or presence of distant metastasis)

    MX: extent of metastasis cannot be determined

    M0: no metastasis

    M1: distant metastasis

  • Site of metastasis may be indicated with parenthetic 3-letter abbreviations:

    ADR

    adrenals

    BRA

    brain

    HEP

    hepatic

    LYM

    lymph nodes

    MAR

    bone marrow

    OSS

    osseous

    OTH

    others

    PER

    peritoneum

    PLE

    pleura

    PUL

    pulmonary

    SKI

    skin

    Example:

    M1(PUL)

The TNM System and Cancer Staging.

Various combinations of the T, N, and M categories are used to define cancer stages (consult the AJCC or UICC manuals for specifics). For example, a TNM stage grouping that defines stage I for many types of cancer is

T1N0M0

The combinations that define individual stages differ among anatomic sites, for example:

lung cancer, stage IIA: T1N1M0

pancreatic cancer, stage IIA: T3N0M0

More than one combination of the T, N, and M categories may constitute the definition of a single stage: eg, in a given cancer, stage III may be defined as T1N1M0 or T2N1M0 or T3N0M0 or T3N1M0.

Optional Descriptors.

Additional descriptors, although not part of the TNM staging system, may be used as adjuncts to the T, N, and M categories for defining the extent of disease; these are indicated by capital letters as follows:

certainty factor (C-factor)

C1, C2, C3, C4, C5

histopathologic grading

GX, G1, G2, G3, G4

lymphatic vessel invasion

LX, L0, L1

residual tumor

RX, R0, R1, R2

venous invasion

VX, V0, V1, V2

C-factor terms may be used together with T, N, and M categories, eg, T3C2, N2C1, M0C2 (example from Sobin and Wittekind3[p15]).

Lowercase prefixes to the T, N, M, and other symbols may be used to indicate the mode of determining criteria for tumor description and staging or other attributes; these are as follows:

a

autopsy

c

clinical

p

pathologic

r

recurrent tumor

y

classification during or after multimodality treatment

Examples: cTNM, pT3

The T, N, M, and other symbols used in cancer staging may be followed by suffixes in addition to the common X, 0, and numerals, which further specify qualities such as size, invasiveness, and extent of metastasis, eg:

Ta

T2a

M1a

N1a

pN1a

pN0

Tis

T2(m)

M2a

N2a

pN1mi

pN0(i)

T1b

T2(5)

N2b

pN0(sn)

pN0(i+)

T1c

T3a

N2c

pN3c

pN0(mol)

T1a1

pN0(mol+)

(m indicates multiple primary tumors at a single site; mi, micrometastasis; sn, sentinel node status; i, isolated tumor cells; mol, isolated tumor cells demonstrated by nonmorphologic [eg, molecular] techniques.)

Examples of such combined terms are

pN0(i)(sn)

pT2cN1cM0

Usage.

Terms such as “stage I cancer,” “TNM staging system,” and “T1N1M0” are widely recognized and may be used in articles without expansion. However, authors should specify the clinical and/or pathologic criteria that define any stage (optionally but preferably citing the staging system of the AJCC or UICC manuals).

Use terms as follows (see also 11.1, Correct and Preferred Usage, Correct and Preferred Usage of Common Words and Phrases [Case, Client, Consumer, Patient, Subject]):

Correct

Incorrect

T category

T stage

N category

N stage

M category

M stage

stage III cancer, patient with stage III cancer

stage III patient

N1 lesions

N1 patients

patients with T1N0M0 tumor, T1N0M0 tumors, T1N0M0 cases

T1N0M0 patients

TXN0M0 classification

For some sites, the histologic grade has been integrated into the staging system.

Other Staging Systems and the TNM System.

The AJCC-UICC TNM classification and stage grouping is not the only system used for staging cancer, and equivalency of the same stage number among different systems cannot be assumed. However, 2 cancer staging systems, the FIGO (International Federation of Gynecology and Obstetrics; http://www.figo.org) staging system for gynecologic cancers10,11 and the Dukes stage system for colon and rectal cancers,12,13 have virtual equivalence with the AJCC-UICC stage. The AJCC-UICC system contains subsets of TNM classifications within stage groups that provide greater prognostic precision within each stage for colorectal cancer than does the Dukes system.12,13

FIGO stages are expressed similarly to TNM stages:

stage I

stage IA

stage IA1

stage IB

stage IB1

stage IC

stage II

stage IIA

stage IA2

stage IIB

stage IB2

stage IIC

stage III

stage IIIA

stage IIIB

stage IIIC

stage IV

stage IVA

stage IVB

Dukes stages are expressed with letters:

Dukes A

or

Dukes stage A

Dukes B

or

Dukes stage B

Dukes C

or

Dukes stage C

Dukes D

or

Dukes stage D

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