Diagnosis of Perihilar Osteoclast Giant Cell Carcinoma in an Elderly Patient: A Report of Diagnostic Challenges Over Several Attempts.

Cholangiocarcinoma is a rare gastrointestinal malignancy with an annual incidence of 0.3 to 6 cases per 100,000, and, usually, it is reported as adenocarcinoma in about 95% of the cases. It can develop as a result of combination of genetic predispositions and various risk factors like but not limited to choledochal cysts, cholelithiasis/choledocholithiasis, yet its diagnosis is challenging due to difficulties in obtaining tissue for diagnosis. In this study, we present a challenging case in diagnosis that reveals undifferentiated carcinoma with osteoclast-like giant cells in the perihilar region of the bile duct.