title: A resected case of two branch duct-type intraductal papillary mucinous neoplasms showing different clinical courses after a two-year follow-up.
abstract: The patient was a 60-year-old man without any particular complaints, but he underwent abdominal computed tomography (CT) and magnetic resonance cholangiopancreatography (MRCP) due to a fatty liver, which revealed two similar cystic lesions regarded as branch duct-type intraductal papillary mucinous neoplasm (BD-IPMN) in the pancreatic body [BD-IPMN (b), 16 mm in size] and tail [BD-IPMN (t), 13 mm in size] without a "high-risk stigmata" or "worrisome features". He subsequently received follow-up by MRCP every 6 months. Two years later, MRCP showed prominent dilation of the main pancreatic duct (MPD) and mural nodule formation within the dilated MPD adjacent to the BD-IPMN (b). Distal pancreatectomy specimens revealed that the BD-IPMN (b) was lined by low-papillary gastric mucinous epithelium with low-to-intermediate-grade dysplasia and involved the MPD, forming a malignant mural nodule showing pancreatobiliary-type IPMN. In contrast, the BD-IPMN (t) was lined by flat, monolayer columnar gastric mucinous epithelium without atypia, which suggested the possibility of a "simple mucinous cyst". A genetic analysis showed KRAS mutation only in BD-IPMN (b). Differences in the histological and genetic findings between two similar BD-IPMNs in the present case may suggest what kinds of examinations should be performed in patients with BD-IPMNs without any worrisome features.
authors.affiliation: Department of Pathology, Showa University Fujigaoka Hospital, 1-30 Fujigaoka, Aoba-ku, Yokohama, 227-8501, Kanagawa, Japan. hshibata@med.showa-u.ac.jp.|Department of Pathology, Showa University Hospital, Shinagawa, Tokyo, Japan. hshibata@med.showa-u.ac.jp.|Department of Gastroenterological and General Surgery, Showa University Hospital, Shinagawa, Tokyo, Japan. hshibata@med.showa-u.ac.jp.
authors.forename: Hideki
authors.identifier: http://orcid.org/0000-0001-7552-8975
authors.initials: H
authors.lastname: Shibata
authors.affiliation: Department of Pathology, Showa University Fujigaoka Hospital, 1-30 Fujigaoka, Aoba-ku, Yokohama, 227-8501, Kanagawa, Japan.
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Ohike
authors.affiliation: Department of Pathology, Showa University Fujigaoka Hospital, 1-30 Fujigaoka, Aoba-ku, Yokohama, 227-8501, Kanagawa, Japan.
authors.forename: Tomoko
authors.initials: T
authors.lastname: Norose
authors.affiliation: Department of Pathology, Showa University Fujigaoka Hospital, 1-30 Fujigaoka, Aoba-ku, Yokohama, 227-8501, Kanagawa, Japan.
authors.forename: Tomohide
authors.initials: T
authors.lastname: Isobe
authors.affiliation: Department of Pathology, Showa University Fujigaoka Hospital, 1-30 Fujigaoka, Aoba-ku, Yokohama, 227-8501, Kanagawa, Japan.
authors.forename: Reika
authors.initials: R
authors.lastname: Suzuki
authors.affiliation: Department of Pathology, Showa University Fujigaoka Hospital, 1-30 Fujigaoka, Aoba-ku, Yokohama, 227-8501, Kanagawa, Japan.
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Imai
authors.affiliation: Department of Pathology, Showa University Fujigaoka Hospital, 1-30 Fujigaoka, Aoba-ku, Yokohama, 227-8501, Kanagawa, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Shiokawa
authors.affiliation: Department of Pathology, Showa University Hospital, Shinagawa, Tokyo, Japan.
authors.forename: Masafumi
authors.initials: M
authors.lastname: Takimoto
authors.affiliation: Division of Gastroenterology, Department of Internal Medicine, Showa University Fujigaoka Hospital, Yokohama, Kanagawa, Japan.
authors.forename: Akihiro
authors.initials: A
authors.lastname: Tabuchi
authors.affiliation: Division of Gastroenterology, Department of Internal Medicine, Showa University Fujigaoka Hospital, Yokohama, Kanagawa, Japan.
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Takano
authors.affiliation: Division of Gastroenterology, Department of Internal Medicine, Showa University Fujigaoka Hospital, Yokohama, Kanagawa, Japan.
authors.forename: Eiichi
authors.initials: E
authors.lastname: Yamamura
authors.affiliation: Division of Gastroenterology, Department of Internal Medicine, Showa University Fujigaoka Hospital, Yokohama, Kanagawa, Japan.
authors.forename: Masatsugu
authors.initials: M
authors.lastname: Nagahama
authors.affiliation: Department of Radiology, Showa University Fujigaoka Hospital, Yokohama, Kanagawa, Japan.
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Takeyama
authors.affiliation: Department of Gastroenterological and General Surgery, Showa University Fujigaoka Hospital, Yokohama, Kanagawa, Japan.
authors.forename: Kazuaki
authors.initials: K
authors.lastname: Yokomizo
authors.affiliation: Department of Gastroenterological and General Surgery, Showa University Fujigaoka Hospital, Yokohama, Kanagawa, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Mizukami
authors.affiliation: Department of Gastroenterological and General Surgery, Showa University Fujigaoka Hospital, Yokohama, Kanagawa, Japan.
authors.forename: Jun-Ichi
authors.initials: JI
authors.lastname: Tanaka
authors.affiliation: Department of Gastroenterological and General Surgery, Showa University Hospital, Shinagawa, Tokyo, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Aoki
authors.affiliation: Department of Gastroenterological and General Surgery, Showa University Hospital, Shinagawa, Tokyo, Japan.
authors.forename: Masahiko
authors.initials: M
authors.lastname: Murakami
mesh_terms: D021441:Carcinoma, Pancreatic Ductal / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009093:Mucus / Q000378:metabolism; D010183:Pancreatic Ducts / Q000000981:diagnostic imaging / Q000473:pathology; D010190:Pancreatic Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D014057:Tomography, X-Ray Computed
keywords: Brunch duct-type IPMN; KRAS mutation; Malignant mural nodule; Simple mucinous cyst