Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: There is subtle increased opacity at the left lung base with subtle opacity in the retrocardiac region and overlying the spine on the lateral view as well . Elsewhere , the lungs are clear . The cardiomediastinal silhouette is within normal limits . Deformity of the left posterior ninth ribs suggest prior healed fracture .
    OUTPUT:
    
Subtle left basilar opacity which could represent pneumonia in the proper clinical setting .