Intraductal oncocytic papillary neoplasm of the bile duct: ultrasonography and CT findings with pathological correlations

Abstract

Papillary tumours of the bile ducts are characterized by an intraluminal papillary mass in association with bile duct obstruction and dilatation. Some of these tumours secrete an excessive amount of mucin, which may disturb bile flow and cause severe ductal dilatation. The condition currently is most commonly described as intraductal papillary mucinous tumour or neoplasm (IPMN) of the bile ducts. In 1996, Adsay et al. proposed the term, intraductal oncocytic papillary neoplasm (IOPN) for a distinctive cystic intraductal tumour with oncocytic features and mucin production as a subtype of IPMN of the pancreas. However, oncocytic (i.e., eosinophilic) changes are extremely rare in the biliary system. To our knowledge, fewer than 10 cases of IOPN of the liver have been reported previously. As the diagnostic concept of IOPN of the biliary system is a relatively recent introduction and the frequency of this diagnosis is increasing, radiologists need to be familiar with this entity. In this report, two cases of IOPN of the bile duct, comprising a unilocular cystic mass with mural nodules, are presented. The radiological features on ultrasonography (US) and computed tomography (CT) are illustrated and correlated with the pathological findings.