Biliary cystic tumors with bile duct communication: a cystic variant of intraductal papillary neoplasm of the bile duct.

Biliary cystic tumors, which are also called biliary cystadenoma and cystadenocarcinoma, are thought to be a heterogeneous disease entity, and some of them are known to show a luminal communication to the bile duct. In this study, we examined the clinicopathological features of nine cases of biliary cystic tumors with bile duct communication. They were composed of five males and four females with an average age of 67 years (52-84 years). They were multilocular (eight cases) or unilocular (one case), and all cases contained mucinous fluid. A direct luminal communication with the bile ducts was identified in five cases on preoperative or intraoperative cholangiographies. Biliary cystic tumors examined in this study were histologically adenoma (one case), adenocarcinoma in situ (six cases), and adenocarcinoma associated with microinvasive mucinous carcinoma (two cases). One case of adenocarcinoma in situ also had the adenoma component (adenocarcinoma in adenoma). Dysplastic mucinous epithelium proliferated in flat, micropapillary and papillary fashions within the intracystic spaces. Intraepithelial neoplasm was observed within non-dilated adjacent bile ducts, suggesting a direct luminal communication between the cystic tumors and the bile duct. Ovarian-like stroma was not observed in their walls in any cases. Immunohistochemically, seven cases expressed MUC1 or MUC2 in the neoplastic biliary epithelium. All cases except one were alive without any evidences of tumor recurrence after total excision (3-156 months after surgery). These clinicopathological features resembled those of intraductal papillary neoplasm of the bile duct, which had been reported as a biliary counterpart of pancreatic intraductal papillary mucinous neoplasm. In conclusion, biliary cystic tumors with bile duct communication could be regarded as intraductal papillary neoplasm with a prominent cystic dilatation of the bile duct and mucin retention, rather than true biliary cystic neoplasms.