HEPATOBILIARY CYSTADENOMA - A STUDY OF 5 CASES WITH REFERENCE TO HISTOGENESIS

Hepatobiliary cystadenoma is a rare hepatic lesion characterized by a multiloculated cyst lined by cuboidal or columnar epithelial cells. Fo ur cases of hepatobiliary cystadenoma with mesenchymal stroma (HCMS) a nd one case of hepatobiliary cystadenoma with intracystic epithelial c omponent were studied by light microscopy, immunohistochemical methods , and electron microscopy. Similar studies were conducted on six fetal gallbladder tissues, representing the biliary tree, and two adult ova rian tissues. By light microscopy, the columnar epithelium of the five cases of hepatobiliary cystadenoma was similar to the epithelium of t he developing gallbladder. The spindle cell stroma of the HCMS and the subepithelial spindle cells of the developing gallbladders showed sim ilar reactivity to smooth-muscle actin. Vimentin reactivity was strong ly positive in the stroma of the HCMS, and in the fetal gallbladders i t was only noted in the subepithelial spindle cells of the 15-week ges tation fetal gallbladder tissues. By electron microscopy, the epitheli um lining the hepatic lesions showed characteristic gastrointestinal f eatures and was identical to the epithelia lining the embryonic gallbl adders. Furthermore, the mesenchymal stroma of the HCMS recapitulated the features found in subepithelial tissues in developing gallbladders . Although the ovarian stroma resembled the stroma of the HCMS by ligh t microscopy, the immunohistochemical reactions and the electron micro scopic studies showed dissimilarities. This study supports the hypothe sis that the hepatobiliary cystadenomas arise from ectopic embryonic t issues destined to form the adult gallbladder.