Superficial vs deep pancreatic parenchymal invasion in the extrahepatic bile duct carcinomas: a significant prognostic factor

Pancreatic invasion of the extrahepatic bile duct (EBD) carcinomas is known to have a poor outcome. We hypothesized that EBD carcinoma showing shallow invasion to the pancreas may have a better outcome than the usual deep pancreatic invasion. We divided 87 cases of the distal EBD carcinomas into superficial and deep pancreatic invasion groups according to degrees of the pancreatic invasion. The superficial pancreatic invasion group included cases with tumor abutting the pancreatic lobule or pancreatic parenchymal invasion equal to or less than 1 mm from the uppermost portion of the pancreatic lobule or tumors invading into the fibroadipose tissue between pancreatic lobules without parenchymal invasion. The deep invasion group consisted of tumors with more than 1 mm pancreatic parenchymal invasion. The cases with superficial pancreatic invasion showed significantly better survival rate than those with deep pancreatic invasion (P<0.001). Therefore, we recommend that a specific remark on the pathology report about the presence or absence of parenchymal invasion and the depth of invasion of the pancreas is required for managing patients and determining the prognosis. We also recommend that the current pT3 stage of distal EBD carcinomas be subdivided into superficial (pT3a) and deep pancreatic invasion (pT3b).