Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The cardiomediastinal and hilar contours are stable . The lungs are hyperinflated as before consistent with COPD . Subtle opacity involving the left mid lung is slightly increased from the prior chest radiograph on ___ and may represent a focus of infection . No pleural effusion or pneumothorax .
    OUTPUT:
    
Persistent opacity in the left mid lung is slightly increased from the prior examination and may represent a focus of infection .