Adenosquamous Carcinoma of the Distal Common Bile Duct: A Case of a Rare Type of Cholangiocarcinoma

INTRODUCTION: Adenosquamous carcinoma (ASC) is a rare subtype of the conventional adenocarcinoma of the bile duct. The clinico-pathological characteristics of this entity are poorly understood partly due to its rarity. CASE SUMMARY: A 67-year-old ASA II male presented with obstructive jaundice subsequently complicated by cholangitis. CT abdomen showed dilatation of the intra and extrahepatic biliary tree. Endoscopic retrograde cholangiopancreatography revealed a stricture with a mucosal growth at the ampulla of Vater. He had a pancreaticoduodenectomy and the distal common bile duct tumour identified in the specimen was on histology an adenosquamous carcinoma (ASC) of the extrahepatic bile duct. DISCUSSION: ASCs are considered to have more aggressive tumour biology compared to adenocarcinomas. The presence of a squamous component at the invasive front relates to its poor prognosis. Surgery is the curative option, but with a high propensity for early recurrence and distant metastases. The scarcity of reports on the clinicopathological course of ASC have resulted in a lack of standardised care pathways. CONCLUSION: A better understanding of the clinicopathological characteristics, biological behaviour and disease progression of ASC will aid therapeutic options and prognostication.