title: Intraductal papillary-mucinous tumors of the pancreas.
abstract: OBJECTIVE
  To elucidate the risk of malignancy and the morphological alterations associated with malignancy.
  
  
  METHODS
  Thirty cases of intraductal papillary-mucinous tumors and 5 papillary-mucinous carcinomas (invasive intraductal papillary-mucinous tumors) of the pancreas were clinicopathologically and histopathologically analyzed.
  
  
  RESULTS
  The invasive carcinoma developed on the basis of severe dysplasia-carcinoma in situ changes and never from mild or moderate dysplasia changes. However, tumor cell projections of intraductal papillary-mucinous tumors encroached into the duct wall and/or the stroma introduced just beneath the epithelium and "intraductal" tumor cells sometimes came in direct contact with the "extraductal" connective tissues even in adenomas. The frankly invasive adenocarcinoma components of invasive intraductal papillary-mucinous tumors were characterized by the lack or poor formation of their own basement membrane and were usually surrounded by the extensive collagenous proliferation, desmoplastic reaction. Such stromal alterations never developed around the "extraductal" components of non-invasive intraductal papillary-mucinous tumors.
  
  
  CONCLUSIONS
  The risk of malignancy for an individual intraductal papillary-mucinous tumor was increased with the degree of cellular and/or structural atypia. The desmoplastic reaction with poor formation of the basement membrane is the sine qua non of the "true invasion".
authors.affiliation: Department of Pathology, Chiba Municipal Hospital, Funabashi Municipal Medical Center, Japan. hitokub@yahoo.co.jp
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Kubosawa
authors.forename: Toshitaka
authors.initials: T
authors.lastname: Uehara
authors.forename: Yoshiji
authors.initials: Y
authors.lastname: Watanabe
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Urashima
authors.forename: Hisahiro
authors.initials: H
authors.lastname: Matsubara
authors.forename: Takehide
authors.initials: T
authors.lastname: Asano
authors.forename: Takenori
authors.initials: T
authors.lastname: Ochiai
mesh_terms: D002288:Adenocarcinoma, Mucinous / Q000145:classification / Q000473:pathology* / Q000601:surgery; D000368:Aged; D021441:Carcinoma, Pancreatic Ductal / Q000145:classification / Q000473:pathology* / Q000601:surgery; D002291:Carcinoma, Papillary / Q000145:classification / Q000473:pathology* / Q000601:surgery; D002455:Cell Division / Q000502:physiology; D002471:Cell Transformation, Neoplastic / Q000473:pathology; D003238:Connective Tissue / Q000473:pathology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009361:Neoplasm Invasiveness / Q000473:pathology; D010179:Pancreas / Q000473:pathology; D010180:Pancreatectomy; D010190:Pancreatic Neoplasms / Q000145:classification / Q000473:pathology* / Q000601:surgery; D011230:Precancerous Conditions / Q000145:classification / Q000473:pathology / Q000601:surgery