Primary biliary tract malignant melanoma: US, CT, and MR findings

We report a case of primary biliary tract malignant melanoma occurring in a 47-year-old male. Ultrasonography and computed tomography showed multiple masses in the gallbladder and distal common bile duct that caused biliary tract dilatation. Magnetic resonance imaging showed that the polypoid masses in the gallbladder and common bile duct were of low signal intensity on T2-weighted images and of high signal intensity on unenhanced T1-weighted images.