Answer: Hepatobiliary cystadenoma

Histology: Much of the bile duct epithelium is ulcerated, and there is a tremendous mixed inflammatory reaction consisting of neutrophils, histiocytes, and plasma cells. Some of the ulcerated epithelium demonstrates reactive atypia which simulates a neoplastic process. Focally, where the epithelium is not ulcerated, one sees a cellular ovarian-like stroma underneath inflamed epithelium. This stroma demonstrates diffuse immunoreactivity for estrogen and progesterone receptors, supporting the diagnosis of hepatobiliary cystadenoma.

Discussion: Papillomatosis could also have multiple areas of ulceration of the bile ducts. However, this is defined by a diffuse, papillary mucinous proliferation of neoplastic epithelium which fills the bile ducts. Choledochal cysts may be markedly ulcerated in adults, likely the result of chronic stasis. This lesion would lack the ovarian-type stroma of hepatobiliary cystadenoma. An infiltrating cholangiocarcinoma would demonstrate irregular glands which infiltrate the stroma of the bile duct.

Hepatobiliary cystadenomas of the extrahepatic bile ducts may be viewed as the biliary analog to mucinous cystic neoplasms of the pancreas. They often are multiloculated, and usually occur in middle-aged females.