Abstract
The patient was a 75-year-old woman who was referred to our hospital for detailed examination of liver dysfunction. Abdominal CT and EUS revealed a mass lesion in the distal bile duct, while ERC showed a filling defect. The patient was preoperatively diagnosed with papillary distal bile duct carcinoma, and surgical resection was performed. Macroscopic findings for the resected specimen included a papillary tumor presenting with redness in the distal bile duct. Histologically, mildly atypical gland and hyperplasia of muscle fibers and fibrous tissue were observed. Based on these findings, a final diagnosis of adenomyomatous hyperplasia was made. Benign tumors rarely occur in the bile duct, and among them, adenomyomatous hyperplasia is particularly rare. As no characteristic findings on diagnostic imaging have been elucidated for this disease, accurate preoperative diagnosis is currently difficult. Detailed investigation through accumulation of cases is necessary in the future.
