It is a developmental anomaly in which abnormal tissues are present at normal site. Due to failure of regression of embryonic billiary duct.
Bile duct hamartoma
Intraductal papillary mucinous neoplasm
Pancreatic serous cystadenoma
Pancreatic mucinous cystadenoma
Pancreatic mucinous cystic neoplasm
Enteric duplication cyst
Accessory bile duct
Choledochal cysts