Adenomas involving the extrahepatic bile ducts are rare benign tumours of the biliary tract. Given the asymptomatic nature of these tumours and the natural progression of biliary adenoma to carcinoma including cholangiocarcinoma, early detection is challenging. We present a case of an octogenarian woman with a remote history of gallstones who initially presented to the gastroenterology office for an incidental finding of biliary dilation, and whose subsequent imagings and biopsy suggested common bile adenoma. However, the patient was deemed a poor surgical candidate for pancreaticoduodenectomy, and unfortunately represented 5 months later with findings suggesting cholangiocarcinoma. This case provides a unique opportunity to study the natural progression of biliary adenoma to cholangiocarcinoma.