A case of choledochal cyst associated with adenocarcinoma exhibiting sarcomatous features.

One complication of choledochal cyst in adulthood is the development of secondary carcinoma, usually well-differentiated adenocarcinoma. We report a case of extrahepatic bile duct carcinoma associated with choledochal cyst and presenting predominantly sarcomatous features. The patient was a 52-year-old female who presented with abdominal fullness and pain. Ultrasound (US), computed tomography (CT), and cholangiography revealed a choledochal cyst with a tumor. The resected choledochal cyst was 10 x 7.5 cm and contained a protruding, ulcerated tumor, measuring about 4.0 x 2.5 cm. Histologically, the tumor was composed of spindle-shaped or fusiform cells with occasional pleomorphic or bizarre giant cells and abundant fibrous stroma, similar to malignant mesenchymal tumors. However, further histologic and immunohistochemical examination revealed that the tumor was adenocarcinoma with prominent sarcomatous features. To our knowledge, sarcomatous change in extrahepatic bile duct carcinoma associated with choledochal cyst has not been previously described.