Preoperative Diagnosis of the Bile Duct Traumatic Neuroma by Endoscopic Ultrasound-guided Tissue Acquisition: A Case Report.

Traumatic neuroma of the cystic duct stump is a rare benign lesion that may mimic biliary malignancy, making preoperative diagnosis challenging. We report a case of an enhancing lesion at the cystic duct stump after cholecystectomy that was diagnosed by endoscopic ultrasound-guided tissue acquisition (EUS-TA). Imaging studies revealed an 8-mm enhancing nodule at the cystic duct stump, and endoscopic retrograde cholangiopancreatography showed a unilateral filling defect at the corresponding site. Peroral cholangioscopy demonstrated smooth mucosa without irregular vessels, suggesting a submucosal lesion rather than mucosal malignancy. EUS revealed a well-demarcated, homogeneous hypoechoic mass immediately distal to the origin of the remnant cystic duct. EUS-TA using a 22-gauge needle enabled TA from the lesion. Histopathological examination showed proliferation of spindle-shaped cells with wavy nuclei, and immunohistochemical staining was positive for S-100 protein, confirming the diagnosis of traumatic neuroma. No procedure-related adverse events occurred, and unnecessary surgical resection was avoided. EUS-TA may facilitate preoperative diagnosis of cystic duct stump traumatic neuroma and help guide appropriate management.