| Primary tumor (T) | |||
| T category | T criteria | ||
| TX | Primary tumor cannot be assessed | ||
| T0 | No evidence of primary tumor | ||
| Tis | Carcinoma in situ/high-grade dysplasia | ||
| T1 | Tumor confined to the bile duct, with extension up to the muscle layer or fibrous tissue | ||
| T2 | Tumor invades beyond the wall of the bile duct to surrounding adipose tissue, or tumor invades adjacent hepatic parenchyma | ||
| T2a | Tumor invades beyond the wall of the bile duct to surrounding adipose tissue | ||
| T2b | Tumor invades adjacent hepatic parenchyma | ||
| T3 | Tumor invades unilateral branches of the portal vein or hepatic artery | ||
| T4 | Tumor invades the main portal vein or its branches bilaterally, or the common hepatic artery; or unilateral second-order biliary radicals with contralateral portal vein or hepatic artery involvement | ||
| Regional lymph nodes (N) | |||
| N category | N criteria | ||
| NX | Regional lymph nodes cannot be assessed | ||
| N0 | No regional lymph node metastasis | ||
| N1 | One to three positive lymph nodes typically involving the hilar, cystic duct, common bile duct, hepatic artery, posterior pancreatoduodenal, and portal vein lymph nodes | ||
| N2 | Four or more positive lymph nodes from the sites described for N1 | ||
| Distant metastasis (M) | |||
| M category | M criteria | ||
| M0 | No distant metastasis | ||
| M1 | Distant metastasis | ||
| Prognostic stage groups | |||
| When T is... | And N is... | And M is... | Then the stage group is... |
| Tis | N0 | M0 | 0 |
| T1 | N0 | M0 | I |
| T2a-b | N0 | M0 | II |
| T3 | N0 | M0 | IIIA |
| T4 | N0 | M0 | IIIB |
| Any T | N1 | M0 | IIIC |
| Any T | N2 | M0 | IVA |
| Any T | Any N | M1 | IVB |
