Case #10

Frozen section diagnosis: Bile duct adenoma.

Pathology and comment: Bile duct adenomas are small, subcapsular, benign tumors, macroscopically very similar to small metastases. Histologically they are composed of small bile ducts that may have a swollen epithelium on frozen section. Lack of mitoses and the regularity of the ducts support the frozen section diagnosis of bile duct adenoma. Differential diagnosis (especially intraoperativelly) may be difficult. Metastatic carcinoma usually shows mitotic figures, more dysplastic changes, and invasion of hepatic cords. Cholangiocarcinomas are frequently larger. Von Meyenburg complex is also a benign process and misinterpretation has no consequences for the immediate surgical procedure.