A case of small in situ perihilar cholangiocarcinoma incidentally accompanied by benign bile duct stricture after open cholecystectomy

BACKGROUND: In situ cholangiocarcinoma is difficult to detect by imaging studies. Thus, cholangiocarcinoma is rarely resected with a preoperative definitive diagnosis, especially nonpapillary flat type in situ carcinoma, which is extremely rare. CASE PRESENTATION: A 70-year old man was diagnosed with gallbladder cancer and received open cholecystectomy with lymphadenectomy at a local hospital. Histologically, the tumor was localized in the mucosal layer, and no lymph node metastases were found. Three months later, hilar bile duct stricture due to delayed bile duct ischemia was found. Then, biliary drainage was performed with endoscopic biliary stenting. Three months later, the patient experienced cholangitis with septic shock, and percutaneous transhepatic biliary drainage (PTBD) into the left intrahepatic bile duct was performed. Unexpectedly, the aspiration bile cytology of the PTBD catheter showed malignant cells, and the patient was referred to our clinic for possible surgical treatment. According to additional studies, the hilar bile duct stricture was 3 cm in length. None of the imaging studies detected malignant cells in the bile duct around the hilar stricture. The left portal vein was obstructed due to inadvertent puncture of the PTBD. No findings indicated cholangiocarcinoma. We performed left hepatectomy with caudate lobectomy and extrahepatic bile duct resection. The postoperative course was uneventful. In the final pathology, flat type in situ carcinoma was found at the confluence of the right and left hepatic ducts, which was distant from the biliary stricture. CONCLUSIONS: When a tumor is undetectable but cytology is positive, in situ cholangiocarcinoma may exist; thus, surgery should be carefully considered.