Benign biliary cystadenoma.

Biliary cystadenomas and cystadenocarcinomas are rare. They arise in the liver or, less frequently, from the bile ducts. The characteristic appearance of these lesions in computed tomography and ultrasonography scans, as observed in a 26-year-old woman, is described. The features are similar to those of hydatid disease, and without travel history and the results of stool cultures and serologic tests differentiation may be impossible. Other considerations in the differential diagnosis are also discussed. Surgery is always indicated, because benign and malignant tumours in this area cannot be differentiated radiologically.