Expression of MUC1 and MUC2 and carbohydrate antigen Tn change during malignant transformation of biliary papillomatosis

Aim: Biliary papillomatosis is characterized by papillary proliferations of biliary lining cells without invasion or metastasis. The neoplastic charac ter and biological behaviour of this disease remain still speculative. Thes e issues were examined in this study. Methods and results: Mucin core protein MUC1, MUC2, MUC3, MUC5AC and carboh ydrate antigens (T, Tn and sialosyl Tn) were immunohistochemically examined , using 11 lesions of biliary papillomatosis from seven patients, and five lesions of biliary papillomatosis with foci of carcinoma from four patients . Five cases of papillary intrahepatic cholangiocarcinoma and 12 histologic ally normal livers were used as a control. Patients with biliary papillomat osis alone or with carcinoma were middle-aged or elderly (five men and six women). Microscopically, biliary papillomatosis showed a villous, papillo-t ubular, papillary, or papillovillous pattern with a thin fibrovascular core . Cytologically, they were classifiable into biliary epithelial or pyloric gland-like type. The former was frequent in the cases associated with carci noma. Expression of MUC1, Tn antigen and sialosyl Tn antigen was frequent a nd marked in biliary papillomatosis alone and with carcinoma and also intra hepatic papillary carcinoma. In addition, marked expression of MUC1 and Tn antigen were rather frequent in biliary papillomatosis with carcinoma and i ntrahepatic biliary papillary carcinoma compared with biliary papillomatosi s. MUC2 was rather frequent and marked in biliary papillomatosis alone comp ared to other two disease groups. Focal expression of MUC5AC and MUC2 was r ather frequent and infrequent irrespective of disease group, respectively. Focal expression of Tn antigen was frequent in papillary ICC. Conclusion: Biliary papillumatosis could undergo overt malignant transforma tion along with altered phenotypic expression of MUC proteins and mucin car bohydrate antigens.