Unusual benign focal liver lesions - Findings on real-time contrast-enhanced sonography

Objective. This presentation aims to provide an overview of the manifestations of some unusual benign focal liver lesions (FLLs) on low-acoustic power contrast-enhanced sonography (CES) with a sulfur hexafluoride contrast agent. Methods. The patients were selected retrospectively from 2209 cases with FLLs who had undergone CES examinations for characterization during the past 3 years. The pathologic examinations proved that they were intrahepatic biliary cystadenoma (n = 1), angiomyolipoma (AML; n = 4), lipoma (n = 1), biliary epithelial dysplasia (n = 1), a fungal inflammatory mass (n = 1), tuberculoma (n = 2), an inflammatory pseudotumor (n = 7), sarcoidosis (n = 1), solitary necrotic nodules (n = 2), peliosis hepatis (n = 2), and focal fibrosis after surgery (n = 4). Results. Contrast-enhanced sonography was beneficial in leading to a diagnosis of benignity for some lesions showing hyperenhancement during the arterial phase and sustained enhancement during the portal or late phase, such as liver AML and lipoma. The benign nature of other lesions showing no enhancement during all phases, such as solitary necrotic nodules and focal fibrosis, was also suggestible. On the other hand, for those lesions showing hyperenhancement, isoenhancement, or hypoenhancement during the arterial phase and hypoenhancement during the late phase, including intrahepatic biliary cystadenoma, biliary epithelial dysplasia, infected liver diseases, the inflammatory pseudotumor, sarcoidosis, and peliosis hepatis, the differential diagnosis between benignity and malignancy was difficult, and pathologic tests were mandatory. Conclusions. The CES features of unusual benign FLLs may enrich knowledge when performing CES examinations for characterization and may provide clues for a specific diagnosis of an individual lesion such as liver AML.