| T: primary tumor | |
| TX | Primary tumor cannot be assessed |
| T0 | No evidence of primary tumor |
| Tis | Carcinoma in situ |
| T1a | Tumor limited to ampulla of Vater or sphincter of Oddi |
| T1b | Tumor invades beyond the sphincter of Oddi or into the duodenal submucosa |
| T2 | Tumor invades the muscularis propria of the duodenum |
| T3a | Tumor invades 5 mm or less into the pancreas |
| T3b | Tumor invades more than 5 mm into the pancreas or extends into peripancreatic tissue or duodenal serosa but without involvement of the celiac axis or the superior mesenteric artery |
| T4 | Tumor with vascular involvement of the superior mesenteric artery or celiac axis, or common hepatic artery |
| N: regional lymph nodes | |
| NX | Regional lymph nodes cannot be assessed |
| N0 | No regional lymph node metastasis |
| N1 | Metastasis in 1?2 regional lymph nodes |
| N2 | Metastasis in 3 or more regional lymph nodes |
| M: distant metastasis | |
| M0 | No distant metastasis |
| M1 | Distant metastasis |