Remnant cystic duct cancer with gradual enlargement over two years of follow-up: a case report and literature review.

Objective: Remnant cystic duct cancer is a rare disease, with only a few reported cases. We report a case of remnant cystic duct cancer that gradually increased in size. Patient: A 78-year-old woman with a history of cholecystectomy presented with a gradually enlarging mass at the porta hepatis after laparoscopic liver resection for hepatocellular carcinoma. Results: Diagnostic imaging, including computed tomography and magnetic resonance imaging, showed a mass at the porta hepatis near a surgical staple, which gradually increased in size over two years. Endoscopic ultrasonography revealed a mass in the cystic duct enhanced with perfluorobutane. Resection of the extrahepatic bile duct with choledochojejunostomy was performed. Histopathological examination revealed a well-differentiated adenocarcinoma at the site where the cystic duct protrudes into the common bile duct opening. The patient remains alive two years after surgery without recurrence or metastasis. Conclusion: Remnant cystic duct cancer is extremely rare and often presents at an advanced stage. This case demonstrated a slow, asymptomatic progression, offering new insight into its natural history.