Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The cardiomediastinal silhouette and pulmonary vasculature are unremarkable . In the left perihilar region , there is a subtle opacity that was not definitively seen on the prior examination . This may represent developing pneumonia . There is no pneumothorax or pleural effusion .
    OUTPUT:
    
Subtle left perihilar opacity likely represents developing pneumonia .