Bile duct adenomas are benign bile duct proliferations usually encountered as an incidental finding. Oncocytic
bile duct neoplasms are rare and the majority are malignant. A 61-year-old male with a diagnosis of colorectal
adenocarcinoma was undergoing surgery when a small white nodule was discovered on the surface of the right lobe of his liver. This lesion was composed of cytologically bland cells arranged in tightly packed glands. These cells were immunopositive for
cytokeratin 7, negative for Hep Par 1, contained
mucin, and had a Ki67 proliferation index of 8%. The morphology, immunophenotype, presence of
mucin, and normal appearing bile ducts, as well as the increased Ki67 proliferation rate, were consistent with a
bile duct adenoma with oxyphilic (oncocytic) change. Oncocytic
tumors in the liver are rare; the first described in 1992. Only two
bile duct adenomas with oncocytic change have been reported and neither of them had reported
mucin production or the presence of normal appearing bile ducts within the lesion.