Table 1. The definition of TNM category in American Joint Committee on Cancer (AJCC) 7th and 8th edition staging system and the modified 8th staging system.

TNM category	Stage	Modified stage (by Shi et al.)
AJCC 8th edition
T1, Maximum tumor diameter ≤2 cm	Stage IA, T1 N0 M0	Stage IA, T1 N0 M0
T2, Maximum tumor diameter >2 cm, but ≤4 cm	Stage IB, T2 N0 M0	Stage IB, T2 N0 M0, T1 N1 M0
T3, Maximum tumor diameter >4 cm	Stage IIA, T3 N0 M0	Stage IIA, T3 N0 M0, T2 N1 M0, T1 N2 M0
T4, Tumor involves the CA or the SMA (unresectable primary tumor)	Stage IIB, T1-3 N1 M0	Stage IIB, T3 N1 M0, T2 N2 M0
N0, No regional LN metastasis	Stage III, T_any N2 M0, T4 N_any M0	Stage IIIA, T3 N2 M0
N1, Metastasis in 1–3 regional LNs	–	Stage IIIB, T4 N_any M0
N2, Metastasis in ≥4 regional LNs	Stage IV, T_any N_any M1	Stage IV, T_any N_any M1
M0, No distant metastasis
M1, Distant metastasis
AJCC 7th edition
T1, Tumor limited to the pancreas, ≤2 cm in maximal diameter	Stage IA, T1 N0 M0
T2, Tumor limited to the pancreas, >2 cm in maximal diameter	Stage IB, T2 N0 M0
T3, Tumor extends beyond the pancreas (without involvement of the CA or the SMA)	Stage IIA, T3 N0 M0
T4, Tumor involves the CA or the SMA (unresectable primary tumor)	Stage IIB, T1-3 N1 M0
N0, No regional LN metastasis	Stage III, T4 N_any M0
N1, Regional LN metastasis	Stage IV, T_any N_any M1
M0, No distant metastasis
M1, Distant metastasis

AJCC, American Joint Committee on Cancer; CA, celiac axis; SMA, superior mesenteric artery; LN, lymph node.