[Pancreatic cancer in a patient with congenital agenesis of the dorsal pancreas].

A 65-year-old man with back pain showed a hypovascular lesion of the head of the pancreas on dynamic computed tomography and abdominal ultrasonography. The distal portion of the pancreas was not visible. Endoscopic retrograde cholangiopancreatography revealed pancreatic duct obstruction, and the duodenal minor papilla was not visible. Therefore, we diagnosed the patient's condition as stage IVa pancreatic cancer with congenital agenesis of the dorsal pancreas. The patient underwent successful chemotherapy with 3 courses of gemcitabine and S-1, which was followed by pancreaticoduodenectomy. Pathological staging revealed invasive ductal carcinoma, pT3, pN0, pM0, stage III. We report a rare case of pancreatic cancer with congenital agenesis of the dorsal pancreas.