Biliary Adenofibroma Presenting as a Hyperenhancing Solid-Cystic Liver Mass: A Case Report

Biliary adenofibroma (BAF) is an extremely rare tumor, with fewer than 30 reported cases since it was first described in 1993. It is classified as a benign biliary neoplasm according to the 2019 World Health Organization tumor classification. However, malignant transformation has been reported, necessitating periodic follow-up or surgical resection in some cases. Due to its rarity, the cross-sectional imaging findings of BAF remain unclear. Various imaging features, such as multilocular cystic, solid cystic, and solid masses, have been described; however, most reported tumors are cystic or solid cystic. The biological behavior of BAF cannot be reliably predicted using imaging features alone, although a few studies have described imaging characteristics suggestive of benign and malignant forms. Pathologically, BAF shares similar features with the von Meyenburg complex but typically presents as a larger lesion. Previous reports have described features associated with malignant BAF, including epithelial components with architectural complexity, an increased Ki-67 proliferation index, and specific gene mutations. We present a case of BAF in a middle-aged female who demonstrated arterial-phase hyperenhancement, washout, and bright T2 signal intensity. The patient underwent wedge resection, and the lesion was pathologically confirmed as a BAF with mild atypia and mild elevation of the Ki-67 proliferation index.