Colorectal cancer (TNM staging 7th edition)

Last revised by Dr Morten Hagir on 04 May 2022

The 7th edition of the TNM classification of colorectal carcinomas was proposed in 2010, and has now been updated and replaced by the 8th edition, published in 2016.

  • 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
  • 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
  • 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
  • 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

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