A case of biliary adenofibroma with malignant transformation.

Identifying precursor lesions of cholangiocarcinoma (CC) is relevant for early diagnosis and management. While for distal, perihilar and large duct cholangiocarcinoma, premalignant lesions are being recognized and studied actively, precursors of peripheral CC are still poorly described. Biliary adenofibroma is a rare benign tumor that has been proposed as a possible precursor lesion of peripheral CC. In the present report, we describe a unique case of a peripheral ICC that originated from a benign biliary adenofibroma with areas of atypical papillary proliferation, which is an expression of a multistep process of carcinogenesis.