Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: There is retrocardiac opacity concerning for pneumonia , best seen on the lateral view . No pleural effusion or pneumothorax is seen . The cardiac and mediastinal silhouettes are unremarkable .
    OUTPUT:
    
Retrocardiac opacity , concerning for pneumonia , likely left lower lobe . Repeat chest radiograph ___ weeks following antibiotic therapy is recommended .