FINDINGS:
Left lower lobe opacity obscuring the left heart border is seen
 only on frontal projection and is likely from the epicardial fat pad  is a
  effect from ribs.  No additional focal opacity, pneumothorax, pulmonary
 edema  pleural effusion.  Heart size, mediastinal and hilar contours are
 normal.  No bony abnormality.

IMPRESSION:
Left lower lobe opacity is likely epicardial fat pad  
 effect from ribs, and is less likely to be pneumonia.