Clinicopathologic Study of Biliary Intraepithelial Neoplasia in Cholangiocarcinoma.

<bold><italic>Backgrounds and Aims:</italic></bold> Biliary intraepithelial neoplasia (BilIN) is a precursor of cholangiocarcinoma (CC) and it has been associated with several chronic inflammatory conditions. This study aimed to elucidate the prevalence of BilIN in CC and its clinicopathological significance. <bold><italic>Methods:</italic></bold> Medical records of 193 patients with histologically confirmed CC were analyzed. We reviewed the pathology findings of 48 patients who underwent curative surgery for CC. <bold><italic>Results:</italic></bold> Of the 48 patients analyzed, 34 and 14 patients had extrahepatic and intrahepatic CC respectively. BilIN was detected in 28 patients (58%) and showed a significantly higher prevalence in extrahepatic CC (75%) than in intrahepatic CC (21%; <italic>p</italic> < 0.001). In the subgroup of 34 patients with extrahepatic CC, 25 and 9 patients were BilIN positive and negative respectively. Poor differentiation and T3 stage were significantly more common in the BilIN-negative group than in the BilIN-positive group (<italic>p</italic> < 0.05). The expression of MUC5AC, p53, and loss of Smad4 showed no difference between BilIN-positive CC and in BilIN-negative CC, but the Ki-67 expression was significantly higher (<italic>p</italic> < 0.05). <bold><italic>Conclusion:</italic></bold> BilIN-positive CC showed less invasiveness than negative cases. The Ki-67 expression was significantly higher in BilIN-positive CC. [ABSTRACT FROM AUTHOR]