Poor prognosis of common-type invasive ductal carcinomas that originate in the branching pancreatic duct.

Purpose: To clarify the incidence, clinicopathological features and prognosis of pancreatic invasive ductal carcinomas (IDCs) with different tumor origin sites in the pancreatic duct.

Methods: Based on the relationship between the invasive cancer area (ICA) and the main pancreatic duct (MPD), IDCs less than 2 cm in diameter were classified into two groups: type I, in which the ICA and MPD were separated, and type II, in which the MPD passed through the ICA. The clinicopathological findings and prognosis of each type were compared in a total of 37 patients.

Results: The incidences of IDC types I and II were 18.9 and 81.1 %, respectively. Although there was no difference in local invasion, both node involvement and venous invasion tended to occur more frequently in type I IDC, and the three-year survival rate was significantly lower for type I (28.6 %) than type II (71.8 %) IDC.

Conclusions: The prognosis of IDCs that originated in the branching pancreatic duct (BPD) distant from the MPD (type I) was worse than the prognosis of IDCs that originated in either the MPD or the BPD close to the MPD (type II). These data suggest that the progression and degree of malignancy of IDCs may vary depending on the site of tumor origin in the pancreatic duct.