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Adenomyoma of the common bile duct: a rare lesion diagnosed and treated by ERCP.

Benign biliary tumors are extremely rare, with an incidence ranging from 0.02% to 0.10% based on pathological examination of resected ducts [1]. Adenomyomas are defined as duct-like structures with hyperplasia of smoothmuscle cells. To our knowledge, only 11 cases originating from the common bile duct have been reported to date [2]. Most of the cases have been diagnosed after extensive surgical resections. This report describes a case of an adenomyoma diagnosed and treated by an endoscopic approach. A 50-year-old woman presented with abdominal pain and underwent an abdominal ultrasound, which showed dilatation of the common bile duct. Liver test results were all within the normal range. Magnetic resonance cholangiopancreatography was performed and revealed mild dilatation of the common bile duct, with a small filling defect on the distal portion (●" Fig.1a). Endoscopic ultrasound confirmed dilation of the biliary tree with a well-defined hypoechoic lesion near the papilla measuring 5.2mm (●" Fig.1b). Fine-needle aspirationwasperformed, but because it was challenging to maneuver the needle towards the small lesion, an endoscopic retrograde cholangiopancreatography was performed simultaneously. Access to the biliary tree was achieved via dissection of the infundibulum, as standard cannulation was not successful. Cholangiography demonstrated a filling defect near the papilla (●" Fig.1c). The endoscopic view showed a small polypoid lesion in the distal bile duct (●" Fig.2a), which was resected using biopsy forceps (●" Fig.2b). At the end of the procedure, the distal bile duct was clear with no further obstruction (●" Fig.2c). Results of histopathological analysis were compatible with a diagnosis of adenomyoma. The patient had a satisfactory postprocedural course, and a major surgical intervention was thus avoided. This case demonstrates the importance of combining direct visualization, diagnostic imaging, and histopathological analysis for the successful treatment of biliary lesions, as can be seen in the video (●" Video1).