Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Lungs are fully expanded and clear . No pneumothorax or pleural effusion . Heart size is normal . Marked widening of the left mediastinum is unchanged and corresponds to a known descending thoracic aortic aneurysm . Cardiomediastinal hilar silhouettes are otherwise unchanged and unremarkable . Heart size is normal .
    OUTPUT:
    
No pneumothorax or other acute cardiopulmonary abnormality . Unchanged widening of the left mediastinum corresponds to a known descending thoracic aortic aneurysm .