Table 1.

TNM staging of colorectal cancer (based on American Joint Committee on Cancer Cancer Staging Manual, 7th edition)

Stage	Finding
Tumour
Tx	Primary tumour cannot be assessed
T0	No evidence of primary tumour
T1	Tumour invades submucosa
T2	Tumour invades muscularis propria
T3	Tumour invades through muscularis propria into perirectal tissues
T4a	Tumour penetrates to surface of visceral peritoneum
T4b	Tumour directly invades or is adherent to other organs or structures
Regional nodal metastases
Nx	Regional nodes cannot be assessed
N0	No regional node metastases
N1	Metastases in 1–3 regional nodes
N2	Metastases in 4 or more regional nodes
Distant metastases
M0	No distant metastases
M1a	Distant metastases confined to one organ/site
M1b	Metastases in more than one organ/site or peritoneum