Table 2.

Summary of TNM/pTNM categories from the last 3 editions of the UICC pTNM system for colorectal carcinoma and the corresponding disease stages^{14,16,17,19,20}

TNM/pTNM categories	4th edition14	5–6th editions (modifications)16,17,19,20
Tx/pTx	Primary tumour cannot be assessed
T0/pT0	No evidence of primary tumour
Tis/pTis	Carcinoma in situ	Carcinoma in situ (intraepithelial or intramucosal, with invasion of lamina propria)
T1/pT1	Tumour invades submucosa
T2/pT2	Tumour invades muscularis propria
T3/pT3	Tumour invades through muscularis propria into subserosa or into non-peritonealised pericolic or perirectal tissues
T4/pT4	Tumour directly invades other organs or structures and/or perforates visceral peritoneum*
Nx/pNx	Regional LNs cannot be assessed
N0/pN0	No regional LN metastasis
N1/pN1	Metastasis to 1–3 pericolic or perirectal LNs	Metastasis to 1–3 regional LNs
N2/pN2	Metastasis to 4 or more pericolic or perirectal LNs	Metastasis to 4 or more regional LNs
N3/pN3	Metastasis to LNs along the course of a named vascular trunk	No N3/pN3 category
Mx/pMx	Distant metastasis cannot be assessed
M0/pM0	No distant metastasis
M1/pM1	Distant metastasis

Disease stages	4th edition14	5th edition19,20	6th edition16,17
*Adherence to other structures or organs must be proved by histology for a pT4 classification: a grossly adherent tumour with no microscopic evidence of adherence is T4, but pT3.
LN, lymph node.
Stage 0	Tis N0 M0	Tis N0 M0	Tis N0 M0
Stage I	T1–T2 N0 M0	T1–T2 N0 M0	T1–T2 N0 M0
Stage II	T3–T4 N0 M0	T3–T4 N0 M0	Stage IIA: T3 N0 M0
			Stage IIB: T4 N0 M0
Stage III	Any T N1–N3 M0	Any T N1–N2 M0	Stage IIIA: T1–T2 N1 M0
			Stage IIIB: T3–T4 N1 M0
			Stage IIIC: any T N2 M0
Stage IV	Any T any N M1	Any T any N M1	Any T any N M1