Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: PA and lateral views of the chest were obtained . On the lateral view , there is a retrocardiac opacity in the left lower lobe which could represent a focus of pneumonia or atelectasis . Otherwise , the lungs are clear . No pleural effusion or pneumothorax . Heart size and mediastinal contours are normal . Bony structures are intact . No free air below the right hemidiaphragm is seen .
    OUTPUT:
    
Band - like opacity in the left lower lobe could represent an early pneumonia or atelectasis .