Clinicopathological subclassification of biliary cystic tumors: Report of 4 cases with a review of the literature.

Biliary cystic tumors are rare hepatic neoplasms, and knowledge regarding the origin and pathology of these tumors remains vague. They should be analyzed in more detail. In our institution, 4 biliary cystic tumor surgeries were performed between December 1999 and March 2010. Pathological evaluation of resected specimens was performed to evaluate the characteristics of the intracystic epithelium and to determine the presence or absence of interstitial infiltrate, ovarian mesenchymal stroma (OMS), luminal communication between the cystic tumor and the bile duct, and mucin (MUC) protein expression. We evaluated the following 4 cases: case 1, a 21-year-old woman with a biliary cystadenoma who underwent extended right hepatectomy; case 2, a 39-year-old woman with a biliary cystadenoma who underwent left hepatectomy; case 3, an 80-year-old man with a biliary cystadenoma who underwent left hepatectomy; and case 4, a 61-year-old man with a biliary cystadenocarcinoma revealing papillary proliferation of atypical epithelium and interstitial infiltrates who underwent left hepatectomy. Case 3 had papillary proliferation of the intracystic atypical epithelium but showed interstitial infiltrates. Luminal communication with the bile duct, centrally or peripherally, was found in all 4 cases. Only case 2 showed OMS. Immunohistochemical staining revealed the following findings: cases 1 and 2, MUC1-/MUC2-; case 3, MUC1+/MUC2-; and case 4, MUC1+/MUC2+. It is important to gather information on more cases of biliary cystic tumors because atypical cases were observed, where both OMS and luminal communication with the bile duct were present or absent.