| The prototype of intraductal neoplasm of pancreas and bile duct are intraductal papillary-mucinous neoplasm (IPMN) and intraductal neoplasm of bile duct (IPNB).IPMN can be categorized main or branch duct type by the epicenter of tumor or dilated ducts.The histologic cellular phenotype is classified as intestinal, gastric, and oncocytic type.The most classical prototype of pancreatic IPMN is the main duct type IPMN with exuberant mucin production and the branch duct type IPMN with gastric phenotype.The main duct type IPMN usually exhibit intestinal phenotype epithelium and close to low-grade mucinous neoplasm of appendix, especially when showed exuberant mucin production like mucocele of the appendix.The branch duct type IPMN usually disclose gastric phenotype.These two IPMN correspond to complete degree of differentiation to intestinal and gastric epithelium.However, it is more common to observe the heterogeneity of cellular phenotype, such as mixed intestinal and gastric or gastric and oncocytic, etc.It seems that high-grade dysplasia or invasive carcinoma may occur more frequently in mixed cellular phenotype, which correspond to incomplete degree of differentiation.It can be explained by mucin profile expression in IPMN.The pure intestinal phenotype IPMN show exclusive expression of MUC2 and CDX2 without MUC5AC or MUC6 expression.Contrary, the pure gastric phenotype IPMN usually express MUC5AC and MUC6 without MUC1 or MUC2 immunoreativity.However, it is more common to observe mixed mucin protein expression, such as MUC2,MUC5AC and MUC6 expression that could be interpreted as mixed gastric and intestinal phenotype.When we consider, the tumorigenesis process is dedifferentiation, it may be more reasonable to observe mixed cellular phenotype of IPMN or IPNB.IPNB has been known to have a similarity with IPMN In aspect of histopathologic findings.However, IPNB is different as it showed higher incidence of invasive carcinoma and different cellular phenotype according to anatomic location.The heterogeneity of cellular phenotype in IPNB is more frequent than that of IPMN and it could one of the clues that. ..invasive carcinoma is more common in IPNB than IPMN.The GNAS mutation is common in IPMN or IPNB, especially in intestinal phenotype.However,it should be carefully interpreted as the heterogeneity of cellular phenotype is common in intraductal neoplasm of pancreas and bile duct. |
