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Hepatobiliary/Pancreas Pathology: Poster#220 INTRADUCTAL PAPILLARY NEOPLASM OF THE BILE DUCT CLINICOPATHOLOGICAL STUDY OF 10 CASES

Background and aims: Intraductal papillary neoplasm of the bile duct (IPNB) is a new entity of biliary neoplasm that is characterized by predominant intraductal papillary growth with various degrees of malignant transformation. It has better prognosis compared with conventional cholangiocarcinoma. Although IPNB has been recently added to the WHO classification, preoperative diagnosis is still challenging and the classification system might need refinements. Methods: We retrospectively reviewed clinicopathological features of 10 surgically resected cases of IPNB, which were previously diagnosed as intraductal cholangiocarcinoma or papillary adenocarcinoma of the bile duct from 2008 to 2014. Histologic features are classified into intestinal, gastric, pancreaticobiliary, and oncocytic types as described in the literature, together with invasive growth pattern and immunohistochemistry. Results: Eight tumors (80%) were invasive IPNB and two (20%) were non-invasive. All of the non-invasive cases are IPNB with high-grade dysplasia. Three cases (30%) were cystic type which having a communication to the bile duct lumen. Discussion: Intraductal growth type cholangiocarcinoma (invasive IPNB) showed a worse prognosis than IPNB with high-grade dysplasia. Curative resection is the major treatment and an important favorable factor for long-term survival, especially in patients with early-stage. Due to its rarity, a mechanism of histopathogenesis remains to be studied.