Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: A large retrocardiac mass is again visualized , extending to both sides of the midline , right greater than left , and measuring about 15 cm in greatest transverse dimension . On the lateral view , this projects posterior to the heart , in a location that is typical for hiatal hernias , although no definite air - fluid level is visualized . Cardiac size is difficult to assess in the setting of this large mass which partially obscures the right heart border . Left cardiac contour and position are within normal limits . Lungs are overexpanded , and note is made of attenuation of upper lobe vessels suggestive of emphysema . Linear areas of scar or atelectasis are present in both lung bases . Bones are diffusely demineralized .
    OUTPUT:
    
15 cm retrocardiac mass probably represents a hiatal hernia , but no definite air - fluid level is identified to confirm this diagnosis . In the absence of a known history of hiatal or other paradiaphragmatic hernia , consider a CT scan or barium swallow for initial confirmation and to exclude other potential masses in this region . Severe upper lobe predominant emphysema .