Xanthogranulomatous Cholecystitis Mimicking Biliary Tract Cancer.

We present a 42-year-old man with a 1-month history of painless jaundice, dark urine, clay-colored stools, and a 13.5-kg weight loss. Laboratory tests revealed elevated liver enzymes and CA19-9. Imaging showed dilation of both the intra- and extrahepatic bile ducts, narrowing of the bile duct at the junction of the common bile duct and common hepatic duct, and a hypoechoic mass involving the neck of the gallbladder and the muscularis propria of the duodenum. Examination of the resected gallbladder and perihilar nodes ruled out malignancy and revealed a diffuse inflammatory infiltrate of giant histiocytes with clear, lipid-containing cytoplasm (xanthoma cells), consistent with xanthogranulomatous cholecystitis.