An 11-year-old male patient demonstrating cholangiocarcinoma associated with congenital biliary dilatation.

We herein report an 11-year-old male patient demonstrating advanced cholangiocarcinoma associated with congenital biliary dilatation (CBD). This Japanese boy presented with abdominal pain lasting a few days, and a diagnosis of type IV-A CBD was made based on the findings of imaging studies using ultrasonography, computed tomography, and magnetic resonance imaging. These studies also revealed a wide flat lesion associated with a few small round masses in the dilated choledochus. Intraoperative cholangiography revealed the presence of pancreaticobiliary maljunction of CP type. Malignant cells were found in biopsy specimens from both the flat and polypoid lesions. Because the distal stump of choledochus at anomalous confluent to the pancreatic duct also showed malignant cells, a pyloric preserved pancreaticoduodenectomy with lymph node dissection was thus performed. Lymph node metastasis was found in one of the mesenteric lymph nodes, and vascular invasion was also found in the main tumor lesions of the dilated bile duct. The postoperative course was uneventful, and the patient has been followed with chemotherapy as an outpatient without any evidence of recurrence. To our knowledge, this report is the youngest case of cholangiocarcinoma associated with CBD.