Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: An opacity in the left lower lobe obscures the left heart border and could reflect pneumonia or atelectasis . No pleural effusion or pneumothorax . Heart is normal size . Mediastinal and hilar structures are unremarkable .
    OUTPUT:
    
Left lower lobe opacity could reflect pneumonia or atelectasis depending on the clinical setting .