Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: A subtle retrocardiac opacity could reflect early pneumonia in the appropriate clinical setting . There is no interstitial edema or pleural effusions . Mediastinal and hilar contours are within normal limits . Mild cardiomegaly is similar to prior examination . Calcifications of the descending thoracic aorta are again noted . There is no pneumothorax .
    OUTPUT:
    
Subtle retrocardiac opacity may reflect early pneumonia in the appropriate clinical setting .