Hepatobiliary cystadenoma with mesenchymal stroma in a patient with chronic hepatitis C.

Hepatobiliary cystadenoma was suggested to be uncommon and it is often difficult to make a differential diagnosis. We report a case of a 65-year-old woman who presented with changes in the structure of a cyst that had been observed for the previous 10 years. Diagnostic imaging revealed a 7-cm-diameter cystic lesion with internal septations and papillary projections in her liver. All laboratory test results were normal; however, cystic fluid carcinoembryonic antigen (CEA) and carbohydrate antigen (CA) 19-9 were raised, at 160 ng/ml andover 200,000 U/ml, respectively. Owing to changes in the structure of the cyst and the difficulty of differential diagnosis from cystadenocarcinoma, a complete surgical excision was performed. The histological findings indicated that the tumor consisted of a multilocular cyst lined by glandular cells (with cuboidal or tall columnar cystoplasm), which were immunohistochemically positive for cytokeratin, CEA, epithelial membrane antigen, and CA 19-9. The underlying stroma was composed of proliferating primitive spindle cells which were immunoreactive for vimentin, alpha-smooth muscle actin, muscle-specific actin, and desmin, and resembled ovarian stroma. From these findings, this tumor was diagnosed as hepatobiliary cystadenoma with mesenchymal stroma. Even though the tumor was previously diagnosed as a simple liver cyst, it was necessary to pay special attention to the changes in the structure of the cyst, using ultra sonography and/or computed tomography, bearing in mind hepatobiliary cystadenoma with mesenchymal stroma. The malignant potential of this tumor is stressed, and complete surgical resection is the recommended therapy.