WHO classification of biliary malignancies22–26
| Benign | Premalignant | Malignant |
| Tumours of intrahepatic bile ducts | ||
| Bile duct adenoma | Biliary intraepithelial neoplasia | Intrahepatic cholangiocarcinoma |
| Microcystic adenoma | Intraductal papillary neoplasm | Intraductal papillary neoplasm with associated invasive neoplasia |
| Biliary adenofibroma | Mucinous cystic neoplasm | Mucinous cystic neoplasm with associated invasive neoplasia |
| Premalignant | Carcinoma |
| Tumours of extrahepatic bile ducts | |
| Adenoma | Adenocarcinoma |
| Biliary intraepithelial neoplasia | Adenosquamous carcinoma |
| Intracystic (gall bladder) or intraductal (bile duct) papillary neoplasm | Intracystic (gall bladder) or intraductal (bile duct) papillary neoplasm + associated invasive neoplasia |
| Mucinous cystic neoplasm | Mucinous cystic neoplasm with associated invasive neoplasia |
| Squamous cell carcinoma | |
| Undifferentiated carcinoma | |