title: A natural course of main duct intraductal papillary mucinous neoplasm of the pancreas with lower likelihood of malignancy.
abstract: OBJECTIVE
  Main duct intraductal papillary mucinous neoplasms (IPMNs) of the pancreas include neoplasms with varying likelihood of progression to malignancy. The aim of this study was to investigate a natural course of main duct IPMNs with a lower likelihood of malignancy.
  
  
  METHODS
  Twenty main duct IPMNs with a lower likelihood of malignancy, which was defined as mural nodule of less than 10 mm or no visualized mural nodule, and negative result of cytological examination of pancreatic juice, underwent regular ultrasound every 3 months. Special imaging examinations and additional pancreatic juice cytological examination were performed when necessary. Surgery was considered when a mural nodule enlarged to 10 mm or the cytological examination result indicated malignancy.
  
  
  RESULTS
  During a mean of 70 months, 12 IPMNs (60%) did not progress and 6 (30%) progressed within a lower likelihood of malignancy. The remaining 2 IPMNs (10%) progressed to meet the criteria for resection, underwent surgery, and were demonstrated to be carcinomas.
  
  
  CONCLUSIONS
  Main duct IPMN with a lower likelihood of malignancy was divided into 2 subgroups: neoplasm that progressed and that which did not progress during its natural course. The former should be resected considering its malignant potential, whereas the latter may be managed nonsurgically as long as it stays unchanged.
authors.affiliation: Department of Gastroenterology, Osaka Medical Center for Cancer and Cardiovascular Diseases, Osaka, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Uehara
authors.forename: Osamu
authors.initials: O
authors.lastname: Ishikawa
authors.forename: Kenji
authors.initials: K
authors.lastname: Ikezawa
authors.forename: Natsuko
authors.initials: N
authors.lastname: Kawada
authors.forename: Takuya
authors.initials: T
authors.lastname: Inoue
authors.forename: Rena
authors.initials: R
authors.lastname: Takakura
authors.forename: Yasuna
authors.initials: Y
authors.lastname: Takano
authors.forename: Sachiko
authors.initials: S
authors.lastname: Tanaka
authors.forename: Akemi
authors.initials: A
authors.lastname: Takenaka
mesh_terms: D002288:Adenocarcinoma, Mucinous / Q000000981:diagnostic imaging / Q000473:pathology* / Q000601:surgery; D000368:Aged; D000369:Aged, 80 and over; D021441:Carcinoma, Pancreatic Ductal / Q000000981:diagnostic imaging / Q000473:pathology* / Q000601:surgery; D002291:Carcinoma, Papillary / Q000000981:diagnostic imaging / Q000473:pathology* / Q000601:surgery; D018450:Disease Progression; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010189:Pancreatic Juice / Q000166:cytology; D010190:Pancreatic Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology* / Q000601:surgery; D014463:Ultrasonography