Development of intrahepatic cholangiocarcinoma at the remnant intrahepatic cyst portion 10 years after resection of type IV choledochal cyst.

Complete resection of Todani type IV choledochal cyst (CC) is not possible, because the intrahepatic portion is not resectable. We present a case of intrahepatic cholangiocarcinoma that arose from the remnant CC portion that was located within the liver 10 years after resection. A 59-year-old female patient had undergone resection of type IV CC 10 years ago, leaving large remnant portions of CC at the liver and pancreas. Two and four years after resection of the extrahepatic CC, cholangitis with intrahepatic stones developed hence these episodes were treated with percutaneous transhepatic cholangioscopy. Ten years after the first operation, intrahepatic stones and a new mass were identified in follow-up imaging studies. Because the mass was identified as adenocarcinoma on biopsy, we performed left hepatectomy with redo hepaticojejunostomy. Pathologic examination showed a 4.5-cm-sized moderately differentiated adenocarcinoma arising from the remnant CC with lymph node metastasis. The patient recovered uneventfully and is currently undergoing adjuvant chemotherapy. Our case indicates that the remnant intrahepatic CC can undergo malignant transformation long after resection of CC. Since the intrahepatic CC portion in type IV CC is usually unresectable, wide hepaticojejunostomy and life-long observation with regular imaging study follow-up are highly recommended for prevention and early detection of malignant transformation.