Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The heart is normal in size . The mediastinal and hilar contours appear within normal limits . There are vague medial upper lung opacities bilaterally with small lucencies suggesting air bronchograms but possibly lung cysts . These may be due to the history of prior pneumocystis infection . There is also small focal retrocardiac opacity with cuffed basilar airways . There is no pleural effusion or pneumothorax .
    OUTPUT:
    
Very vague medial upper lung opacities , which may be due to scarring from prior pneumocystis infection , including small cystic areas versus air bronchograms . Active infection is difficult to exclude however . However , small but focal retrocardiac opacity with air thickening may be due to pneumonia or lower airways infection or inflammation in the left lower lobe .