Cystadenoma and cystadenocarcinoma with mesenchymal stroma of the liver. Immunohistochemical analysis.

Cystadenoma with mesenchymal stroma is a rare neoplasm of the liver that occurs exclusively in young women and has a potential for malignant transformation. A light microscopic and immunohistochemical study of a case of biliary cystadenoma and another of biliary cystadenocarcinoma revealed a range of differentiation of the lining epithelial cells. The lining cells in the cystadenoma resembled the cells of the normal intrahepatic bile ducts. In contrast, the epithelial lining in the case of cystadenocarcinoma had features of intestinal mucosa, including goblet, Paneth, and endocrine cells similar to those found in other mucinous cystic neoplasms of the foregut area. The compact "ovarianlike" mesenchymal stromal cells had immunohistochemical characteristics of myofibroblasts. These are reactive contractile cells that may proliferate in response to the expanding cysts and female hormones, and they differ immunohistochemically from ovarian stromal cells.