Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Dense left retrocardiac opacity most likely represent atelectasis . There is mild pulmonary vascular congestion . The lung apices are not captured on the current study , and there may be tiny pneumothoraces , particularly on the right . No sizable pleural effusion on the right . Slight blunting of the left costophrenic angle may represent a small effusion . Heart size is top normal . Ill - defined lucency projecting over the left superior heart border may represent pneumomediastinum . There is extensive subcutaneous emphysema .
    OUTPUT:
    
1 . Incompletely evaluated apices , which may contain small pneumothoraces . 2 . Possible pneumomediastinum . 3 . Small left pleural effusion with adjacent atelectasis . 4 . Extensive subcutaneous emphysema is likely postsurgical .