Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The lungs are clear . The upper mediastinum is widened . The cardiac and hilar margins are normal . There is no pneumothorax or pleural effusion . The pulmonary vascularity is normal .
    OUTPUT:
    
Widened mediastinum of unknown chronicity , possibly due to lymphadenopathy . No hilar lymphadenopathy identified . A chest CT would be definitive in establishing the cause of this abnormality .