Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The lungs are well expanded and clear . Cardiomediastinal and hilar contours are unremarkable . A small nipple - like projection at the level of the aortic knob is a normal radiographic variant and is secondary to a left superior intercostal vein overlying the aortic arch . There is no pleural effusion or pneumothorax .
    OUTPUT:
    
Unremarkable chest radiographic examination .