A 23-year-old female patient with recently diagnosed hepatitis B infection underwent an initial liver US exam. Axial view US image shows a oval-shaped purely cystic lesion (arrows) in the posterolateral aspect of the right liver lobe in close proximity to the right hemidiaphragm (arrowheads). The lesion was found to be representing a diaphragmatic mesothelial cyst. Follow-up studies confirmed the stability of this lesion