Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The lungs are clear . The cardiomediastinal silhouette , hilar contours , pleural surfaces are normal . Note is made of an opacity in the left lower lung base , likely nipple shadow . No pneumothorax , pleural effusion , pulmonary edema , or pneumonia .
    OUTPUT:
    
1 . No pneumonia . 2 . Opacity in the left lower lung base is likely due to nipple shadow , however , a focal mass can not be excluded .