Undifferentiated Carcinoma Arising in a Choledochal Cyst: A Case Report

ABSTRACT

An association between choledochal cyst and carcinoma is well established. Here, we report an extremely rare case of undifferentiated carcinoma exhibiting extensive sarcomatous features arising in a choledochal cyst. The patient in our case had a radiologically confirmed choledochal cyst and anomalous pancreaticobiliary ductal union, and mild wall thickening in the cyst was observed on endoscopic retrograde cholangiopancreatography. The patient underwent common bile duct excision and cholecystectomy. In the choledochal cyst, a nodule measuring 1.5x1 cm was detected. The lesion was composed of atypical, spindle-shaped and large, round pleomorphic tumor cells simulating sarcoma. Neither glandular nor squamous differentiation was observed. These cells were immunoreactive for both vimentin and cytokeratin by immunohistochemistry. These histologic and immunohistochemical findings were consistent with undifferentiated carcinoma, spindle and giant cell type, according to the WHO classification.