Mesenterico-portal vein invasion should be an important factor in TNM staging for pancreatic ductal adenocarcinoma: Proposed modification of the 8th edition of the American Joint Committee on Cancer staging system

Table 4 The 8^th edition of the American Joint Committee on Cancer staging system and the modified staging scheme

AJCC staging of pancreatic cancer (8th edition)	Stage
Primary tumor size and extension (T)
T1: Tumor ≤ 2 cm in the greatest dimension, without involvement of the CA, SMA, and CHA.	IA: T1N0M0
	IB: T2N0M0
T2: Tumor > 2 cm and ≤ 4 cm in the greatest dimension, without involvement of the CA, SMA, and CHA.	IIA: T3N0M0
	IIB: T1-3N1M0
T3: Tumor > 4 cm in the greatest dimension, without involvement of the CA, SMA, and CHA.	III: (1) TxN2M0;
T4: Tumor involves the CA, SMA, or CHA, regardless of size.	(2) T4NxM0
Regional lymph node (N)	IV: TxNxM1
N0: No positive regional lymph node
N1: 1-3 positive regional lymph nodes
N2: 4 or more positive regional lymph nodes
Distant metastasis (M)
M0: No distant metastasis
M1: Distant metastasis
Modified staging of pancreatic cancer
Primary tumor size and extension (T)
T1: Tumor ≤ 2 cm in the greatest dimension, without involvement of the CA, SMA, CHA, and MPV	IA: T1N0M0
	IB: T2N0M0
T2: Tumor > 2 cm and ≤ 4 cm in the greatest dimension, without involvement of the CA, SMA, CHA, and MPV	IIA: T1N1M0
	IIB: T3N0M0;
T3: Tumor involves the MPV, or > 4 cm in the greatest dimension, without involvement of the CA, SMA, and CHA	T2N1M0
	III: (1) T3N1M0;
T4: Tumor involves the CA, SMA, or CHA, regardless of size	(2) TxN2M0;
Regional lymph node (N)	(3) T4NxM0
N0: No positive regional lymph node	IV: TxNxM1
N1: 1-3 positive regional lymph nodes
N2: 4 or more positive regional lymph nodes
Distant metastasis (M)
M0: No distant metastasis
M1: Distant metastasis

AJCC: American Joint Committee on Cancer; CA: Celiac artery; SMA: Superior mesenteric artery; CHA: Common hepatic artery; MPV: Mesenterico-portal vein.