Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: PA and lateral views of the chest were obtained . Vague linear opacity on the frontal view at the left lung base is most likely atelectasis as there is no correlate view on the lateral view . No definite signs of pneumonia or CHF . Cardiomediastinal silhouette is stable . Bony structures are intact . No free air below the right hemidiaphragm .
    OUTPUT:
    
Left lung base atelectasis . No signs of pneumonia .