Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: When compared to prior , there has been no significant interval change . Again seen is retrocardiac opacity with inferior retraction of the left hilum . This has been seen dating back to ___ and is likely due to scarring . Elsewhere , the lungs are clear . The cardiomediastinal silhouette is within normal limits . No acute osseous abnormalities .
    OUTPUT:
    
Chronic retrocardiac opacity suggestive of scarring . No definite superimposed acute cardiopulmonary process .