Intraductal tubulopapillary neoplasm of the bile duct: A case report and review of the published work.

Recent studies have suggested that a peculiar tumor mimicking intraductal tubulopapillary neoplasms (ITPN) of the pancreas can develop in the bile duct. Here, we present a similar case and review the published work on the newly proposed biliary neoplasm. A 68-year-old woman was referred to us for further evaluation of a liver mass. On imaging, the tumor was 40 mm in size and intraductal in location, and was enhanced slightly on the contrast-enhanced computed tomography. No mucin overproduction was found. She underwent right hepatectomy for suspected intraductal papillary neoplasm of the bile duct. The tumor histologically consisted of the biliary-type epithelium arranged in a tubular architecture within the dilated bile duct. Tumor cells had features of high-grade dysplasia but no stroma invasion. No expressions of MUC2 and MUC5AC were noted. On molecular studies, KRAS and GNAS appeared to be wild-type genotypes. These features were in keeping with ITPN. In the published work review, "biliary ITPN" described in four manuscripts were characterized by predominantly intrahepatic/hilar in location, histological tubular architecture, negative expressions of MUC2 and MUC5AC, and uncommon alterations of KRAS, GNAS and BRAF. Although invasive malignancy was present in 71%, the outcome was favorable with the 5-year survival expected to be approximately 90%. Biliary ITPN are supposedly uncommon, but a greater awareness of this condition may give more chance to diagnose the underrecognized neoplasm.