Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Subtle retrocardiac opacity projecting over the lower thoracic spine on the lateral view may relate to vascular structures however , underlying consolidation can not be excluded in the appropriate clinical setting . No pleural effusion or pneumothorax is seen . The cardiac and mediastinal silhouettes are stable .
    OUTPUT:
    
Slight increase in retrocardiac opacity on the lateral view most likely relates to vascular structures , but underlying consolidation is difficult to exclude in the appropriate clinical setting . No diffuse opacity is seen to suggest PCP , ___ , chest CT is more sensitive in evaluating for PCP .