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Intraductal papillary neoplasm of the bile duct diagnosed by upper gastrointestinal endoscopy through a duodenobiliary fistula

Intraductal papillary neoplasms of the bile duct (IPNBs) are a type of intraepithelial neoplasia, involving papillary growth in the bile duct. The 2019 World Health Organization (WHO) classification stated that IPNB was pathologically characterized by dilated bile ducts filled with a non-invasive papillary or villous neoplasms covering delicate fibrovascular stalks [1]. Classical IPNB was typically develops in the intrahepatic bile ducts with rich mucin production. Many cases are composed of high grade dysplasia with not infrequent microscopic foci of low/ intermediate grade dysplasia, and actually, some cases are only composed of low/intermediate dysplasia or adenoma, suggesting multi-step carcinogenesis [2]. Most cases of IPNB are diagnosed by examining surgical specimens. IPNB remains diagnostic challenge [3] [4]. Here, we report a case of IPNB, which was directly diagnosed by performing upper gastrointestinal endoscopy through a duodenobiliary fistula.