Unusual fusion between ventral and dorsal primordia causes anomalous pancreaticobiliary junction

Anomalous pancreaticobiliary junction (APBJ) is a congenital anomaly in which the pancreatic duct joins the common bile duct proximal to the sphincter of Oddi. Anatomical and immunohistochemical examination of the pancreas with APBJ has rarely been performed. A 72-year-old woman with gallbladder cancer and APBJ died of respiratory failure. Macroscopic features of the pancreas were examined in detail. Immunohistochemistry using anti-pancreatic polypeptide (anti-PP) antibody was done to discriminate ventral and dorsal pancreas. Macroscopically the inferior part of the head of the pancreas was smaller than normal. The posterior surface of the head was obliquely grooved. Part of the pancreatic head protruded into the posterior side of the pancreatic head. A PP-rich region was located in the superioposterior position of the pancreas head. Considering the relationship between the ventral and dorsal pancreas, it was inferred that the ventral primordium could obliquely fuse with the dorsal primordium during embryological development. As a result, APBJ occurs through an abnormal fusion between ventral and dorsal primordia.