A Case of Adenomyomatous Hyperplasia of the Distal Common Bile Duct Mimicking Malignant Stricture.

Adenomyomatous hyperplasia is a reactive malformation or non-neoplastic tumor-like lesion frequently observed in the gallbladder, stomach, duodenum and jejunum, but rare in the extrahepatic bile duct. A 42-year-old man with epigastric discomfort had a stricture in the common bile duct on initial CT scans. Initially, it was regarded as a malignant lesion with some evidence, but histopathologic examinations of multiple biopsies obtained by multiple sessions of endoscopic retrograde cholangiopancrea-tography showed no evidence of malignancy. The patient had undergone the pylorus preserving pancreaticoduodenectomy because of the possibility of malignancy; however, the final diagnosis was adenomyomatous hyperplasia. It is important to distinguish a malignancy from benign biliary stricture with endoscopic biopsies. Surgery for suspected biliary malignancy often reveals benign lesions. Therefore, a correct diagnosis is important before deciding upon treatment of bile duct stricture. In conclusion, in younger patients with bile duct stricture where there is no evidence of histologic malignancy despite multiple biopsies, the possibility of benign disease such as adenomyomatous hyperplasia should be considered, to avoid unnecessary radical surgery.