A mucinous cystic neoplasm that arises from the extrahepatic bile ducts. The disease is Monarch Disease Ontology id MONDO_0004462 (extrahepatic bile duct cystadenoma). Also known as: cystadenoma of extrahepatic bile duct, cystadenoma of the extrahepatic bile duct, extrahepatic bile duct mucinous cystic neoplasm.