Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: AP and lateral views of the chest were obtained . The heart is top normal size and cardiomediastinal silhouette is stable . Lungs are symmetrically expanded and clear . A retrocardiac nodular density to the left of the descending thoracic aorta is unchanged . There is no pleural effusion or pneumothorax .
    OUTPUT:
    
No evidence of pneumonia .