The 7th edition of the TNM classification of colorectal carcinomas was proposed in 2010, and has now been updated and replaced by the 8th edition, published in 2016.
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Primary tumor staging (T)
Tx: primary tumor cannot be assessed
T0: no evidence of primary tumor
Tis: carcinoma in situ
T1: into (but not through) submucosa
T2: into (but not through) muscularis propria
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T3
through muscularis propria into subserosa, or
into non-peritonealised pericolic/perirectal tissues
T4a: penetration of the visceral peritoneal layer
T4b: penetration or adhesion to adjacent organs
Nodal status (N)
Nx: nodes cannot be assessed
N0: no evidence of nodal involvement
N1a: involvement of one regional node
N1b: involvement of 2-3 regional nodes
N1c: deposits involving serosa or non-peritonealised pericolic/perirectal tissues without regional nodal metastasis
N2a: involvement of 4-6 nodes
N2b: involvement of ≥7 nodes
Metastases (M)
Mx: presence of metastases cannot be assessed
M0: no evidence of metastases
M1a: distant metastases confined to one organ (e.g. liver, lung, ovary, non-regional node)
M1b: distant metastases confined to more than one organ or to the peritoneum