Biliary Adenofibroma of the Liver: Report of a Case and Review of the Literature

We herein report the clinicopathologic features of a rare case of biliary adenofibroma (BAF) of the liver in a 79-year-old man. Grossly, tumour presented as a well-circumscribed, 5.5-cm mass with a solid and microcystic appearance. Histological examination was typical of biliary adenofibroma, showing a proliferation of variable-sized tubulocystic structures embedded in a moderately cellular fibrous stroma. Immunohistochemistry, revealing immunoreactivity of the epithelial component to cytokeratins 7 and 19, was consistent with a bile duct origin. Notably, the stromal cells had a myofibroblastic profile, showing a diffuse and strong expression of vimentin and -smooth muscle actin. Differential diagnosis with Von Meyenburg complex, biliary adenoma, biliary cistadenoma, congenital biliary cystsy, and hepatic benign cystic mesothelioma is provided. The occasionally reported expression of p53 in biliary adenofibroma has suggested that this tumour could represent a premalignant lesion. The absence of both cytological atypia and p53 immunoreactivity in our case confirms that BAF is a benign tumour with an indolent clinical behaviour. However, a careful histological examination of BAF is mandatory because malignant transformation of the epithelial component has been documented in two cases. 1. Introduction Benign biliary tumours are uncommon, including bile duct adenoma (also known as peribiliary gland hamartoma), biliary hamartoma (von Meyenburg complex), biliary cystadenoma, and the solitary bile cysts.Tsui et al. in 1993 described a new liver tumour entity called “biliary adenofibroma” (BAF) [1]. To the best of our knowledge, only six cases of BAF of the liver have been reported in the literature to date (Table 1) [1–6]. Two of us reported a morphologically similar tumour in equine [7]. BAF is characterized by a proliferation of tubulocystic structures variably embedded in a fibrous stroma. Etiology of BAF is still unknown, even if its immunophenotypic profile (cytokeratins , , , , D , 1F ) suggests a large bile and/or interlobular duct origin [6]. Interestingly, monosomy 22, a cytogenetic alteration found in some benign mesenchymal neoplasms, has been documented in one case of BAF [5]. Although BAF is a benign tumour with a clinical indolent behavior, malignant transformation of the epithelial component [2, 3] with associated distant metastases [3] has been documented. Table 1: Clinical features of BAFs reported in the literature. We herein report the clinicopathological features of a rare case of liver BAF with a benign clinical course after a 7-year