Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The heart is normal in size . The mediastinal and hilar contours appear within normal limits . There is a new opacity in the left lower lobe , in the retrocardiac region , suggesting pneumonia . Otherwise , the lungs remain clear . There is no pleural effusion or pneumothorax . Mild degenerative changes appear similar along the lower thoracic spine .
    OUTPUT:
    
New retrocardiac opacity suspicious for pneumonia .