Intraductal papillary-mucinous tumors of the pancreas.
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".
Kubosawa
Hitoshi
H
Department of Pathology, Chiba Municipal Hospital, Funabashi Municipal Medical Center, Japan. hitokub@yahoo.co.jp
Uehara
Toshitaka
T
Watanabe
Yoshiji
Y
Urashima
Tetsuro
T
Matsubara
Hisahiro
H
Asano
Takehide
T
Ochiai
Takenori
T
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