A woman in her 60's visited our hospital complaining abnormality in medical examination. Pancreatic cysts, adenomyomatosis, a gallbladder stone, and thickened gallbladder wall were detected using abdominal ultrasonography. Detailed investigations, including ERCP, revealed a non-dilated pancreaticobiliary maljunction, with branch-type IPMN and cholecystectomy was performed. Pathological examination revealed adenomyomatosis of the gallbladder at the bottom and cholesterosis in the gallbladder wall. Biliary carcinoma occurs in 42.4% of non-dilated bile duct-pancreatic-biliary junction abnormalities, and 88.1% of these cases are gallbladder carcinoma; therefore, prophylactic cholecystectomy is recommended. However, because this case was diagnosed in an elderly patient, surgery was performed immediately after confirming the absence of malignancy in the biliary system by using EUS and biliary cytology. In addition, the patient also has IPMN, which is considered to be a high risk for pancreatic cancer development. Frequent follow-up of the patient's pancreatic-biliary system function is required.
