Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: PA and lateral views of the chest provided . Subtle opacity in the left lung base is more suggestive of atelectasis though difficult to exclude pneumonia . No large effusion or pneumothorax . Right lung is clear . Cardiomediastinal silhouette is stable . Bony structures are intact .
    OUTPUT:
    
Subtle opacity at the left lung base likely represents atelectasis , less likely pneumonia .