Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Lungs are well expanded bilaterally with ill - defined opacity in the left lower lung also present on the prior study . This could be a scar , but it is not seen well enough to be sure it is unchanged ; instead it needs evaluation as a possible mass , with CT scanning . Lungs are otherwise clear . There is no pleural effusion or pneumothorax . The normal cardiomediastinal and hilar silhouettes are stable .
    OUTPUT:
    
Persistent left lower lung mass warrants CT scanning . No pneumonia .