The TNM Staging System
15.2.2 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+) |
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 |