Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: A retrocardiac opacity is new since ___ . The lungs are hyperexpanded . There is no pleural effusion or pneumothorax . The cardiac and mediastinal contours are stable . Old rib fractures are identified .
    OUTPUT:
    
Retrocardiac opacity concerning for pneumonia in the correct clinical setting . Follow - up to resolution is recommended to exclude an underlying abnormality .