Biologically Different Subgroups of Invasive Ductal Carcinoma of the Pancreas

Abstract

Purpose: Among invasive ductal carcinomas of the pancreas (IDCP), there is a morphologically characteristic subgroup accompanied by abundant intraductal carcinoma components (ICCs). With the aim of determining whether ICC-rich IDCP are biologically different from ICC-poor IDCP, the expression status of Dpc4 protein was analyzed. Experimental Design: A total of 43 IDCP was subdivided into two groups: (a) ICC-rich IDCP (ICCs area occupies ≥10% of the entire tumorous area); and (b) ICC-poor IDCP (with Results: In a total of 43 IDCP, there were 23 ICC-rich IDCP and 20 ICC-poor IDCP. Dpc4-positive immunostaining was observed in the invasive carcinoma component of ICC-rich IDCP, ICC-poor IDCP, and ICs from IPMN in 18 of 23 (78%), 4 of 20 (20%), and 7 of 10 (70%) cases, respectively. In the intraductal component, positive staining for Dpc4 was found in 20 of 23 (87%), 3 of 7 (41%), and 8 of 10 (80%) cases, respectively. Dpc4 expression was found in both the invasive and ICC components of ICC-rich IDCP, similar to that found in IC derived from IPMN, whereas the expression of Dpc4 was largely diminished in ICC-poor IDCP. Conclusions: Morphologically distinct subgroups of invasive ductal carcinomas of the pancreas, namely ICC-rich IDCP and ICC-poor IDCP, are also biologically distinguishable as revealed by the differential expression of Dpc4.