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Biologically Different Subgroups of Invasive Ductal Carcinoma of the Pancreas

Dpc4 Status According to the Ratio of Intraductal Carcinoma Components

¹ Pathology Division and ² Division of Hepatobiliary and Pancreatic Surgery, National Cancer Center Hospital East, Kashiwa, Chiba; ³ Department of Surgery and Clinical Oncology, Graduate School of Medicine, Osaka University, Suita, Osaka; and ⁴ Department of Surgery, Institute of Clinical Medicine, University of Tsukuba, Tsukuba, Ibaraki, Japan

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 <10% of ICCs area). A total of 10 invasive carcinomas derived from intraductal papillary-mucinous neoplasms (ICs from IPMNs) were also analyzed. Each invasive and intraductal carcinoma area was then evaluated for Dpc4 protein status by immunohistochemistry.

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.