Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Increased left basilar retrocardiac opacification is likely due to atelectasis . The known left upper lobe mass is better demonstrated on the prior CT scan . Paramediastinal scarring and fibrosis is unchanged . The lungs are otherwise clear . There is no pneumothorax .
    OUTPUT:
    
No pneumothorax . Increased left basilar retrocardiac atelectasis . Stable paramediastinal radiation fibrosis .