title: A case of MUC5AC-positive intraductal neoplasm of the pancreas classified as an intraductal tubulopapillary neoplasm?
abstract: This report describes a unique case of intraductal tubulopapillary neoplasm (ITPN) of the pancreas in order to clarify its oncogenesis and more precisely classify pancreatic intraductal neoplasms. A 74-year-old man visited our institution for follow-up of acute pancreatitis. Imaging examinations revealed a hypovascular intraductal mass in the head of the pancreas with progressive dilation of the pancreatic duct, atrophy of the pancreatic parenchyma, and a non-mucinous appearance. A pancreatoduodenectomy was performed to identify this pancreatic intraductal neoplasm. Macroscopically, the tumor was a solid nodular mass with no visibly secreted mucin obstructing the dilated ducts. Histologically, it had a homogeneous appearance with nodules of back-to-back tubular glands and occasional papillary elements, and there were no apparent transitions to areas with less marked cytoarchitectural atypia. Although the intraductal neoplastic growth corresponded to an ITPN, immunohistochemical staining revealed partial positivity for MUC5AC, for which ITPNs are characteristically negative. Somatic mutations in KRAS, GNAS, BRAF, and PIK3CA were not detected. A loss of MUC5AC expression and mutations in KRAS and GNAS are key elements in the diagnosis of ITPN. Thus, it was difficult to distinguish the present case as a pancreatobiliary-type (PB-type) intraductal papillary mucinous neoplasm (IPMN) or a phenotypic variant of ITPN. As it is possible that some cases of PB-type IPMN and ITPN overlap, the precise classification of these rare lesions may require re-evaluation.
authors.affiliation: Department of Medicine, Gastroenterology, Shinshu University School of Medicine, 3-1-1 Asahi, Matsumoto 390-8621, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Muraki
authors.affiliation: Department of Laboratory Medicine, Shinshu University School of Medicine, 3-1-1 Asahi, Matsumoto 390-8621, Japan. Electronic address: tuehara@shinshu-u.ac.jp.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Uehara
authors.affiliation: Department of Laboratory Medicine, Shinshu University School of Medicine, 3-1-1 Asahi, Matsumoto 390-8621, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Sano
authors.affiliation: Department of Biomedical Laboratory Sciences, Shinshu University School of Medicine, 3-1-1 Asahi, Matsumoto 390-8621, Japan.
authors.forename: Hiroyoshi
authors.initials: H
authors.lastname: Oota
authors.affiliation: Department of Laboratory Medicine, Shinshu University School of Medicine, 3-1-1 Asahi, Matsumoto 390-8621, Japan.
authors.forename: Akihiko
authors.initials: A
authors.lastname: Yoshizawa
authors.affiliation: Department of Laboratory Medicine, Shinshu University School of Medicine, 3-1-1 Asahi, Matsumoto 390-8621, Japan.
authors.forename: Shiho
authors.initials: S
authors.lastname: Asaka
authors.affiliation: Department of Laboratory Medicine, Shinshu University School of Medicine, 3-1-1 Asahi, Matsumoto 390-8621, Japan.
authors.forename: Ayako
authors.initials: A
authors.lastname: Tateishi
authors.affiliation: Department of Laboratory Medicine, Shinshu University School of Medicine, 3-1-1 Asahi, Matsumoto 390-8621, Japan.
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Otsuki
authors.affiliation: Department of Laboratory Medicine, Shinshu University School of Medicine, 3-1-1 Asahi, Matsumoto 390-8621, Japan.
authors.forename: Kunihiko
authors.initials: K
authors.lastname: Shingu
authors.affiliation: Department of Laboratory Medicine, Shinshu University School of Medicine, 3-1-1 Asahi, Matsumoto 390-8621, Japan.
authors.forename: Hisanori
authors.initials: H
authors.lastname: Matoba
authors.affiliation: Department of Laboratory Medicine, Shinshu University School of Medicine, 3-1-1 Asahi, Matsumoto 390-8621, Japan.
authors.forename: Shota
authors.initials: S
authors.lastname: Kobayashi
authors.affiliation: Department of Laboratory Medicine, Shinshu University School of Medicine, 3-1-1 Asahi, Matsumoto 390-8621, Japan.
authors.forename: Shojiro
authors.initials: S
authors.lastname: Ichimata
authors.affiliation: Department of Medicine, Gastroenterology, Shinshu University School of Medicine, 3-1-1 Asahi, Matsumoto 390-8621, Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Watanabe
authors.affiliation: Department of Medicine, Gastroenterology, Shinshu University School of Medicine, 3-1-1 Asahi, Matsumoto 390-8621, Japan.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Itou
authors.affiliation: Department of Medicine, Gastroenterology, Shinshu University School of Medicine, 3-1-1 Asahi, Matsumoto 390-8621, Japan.
authors.forename: Eiji
authors.initials: E
authors.lastname: Tanaka
mesh_terms: D000368:Aged; D014408:Biomarkers, Tumor / Q000032:analysis; D021441:Carcinoma, Pancreatic Ductal / Q000145:classification / Q000473:pathology*; D002291:Carcinoma, Papillary / Q000473:pathology; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D055271:Mucin 5AC / Q000032:analysis / Q000096:biosynthesis*; D010190:Pancreatic Neoplasms / Q000145:classification / Q000473:pathology*; D016577:Pancreaticoduodenectomy
chemical_list: D014408:Biomarkers, Tumor; C524678:MUC5AC protein, human; D055271:Mucin 5AC
keywords: Intraductal papillary mucinous neoplasm; Intraductal tubulopapillary neoplasm; MUC5AC; Pancreatobiliary type; WHO