Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: There is subtle left basilar opacity , previously seen and improved from ___ . This may represent atelectasis or residual consolidation from possible previous pneumonia . There is no new focal consolidation , pleural effusion , pulmonary edema , or pneumothorax . The heart and mediastinal contours are stable .
    OUTPUT:
    
Subtle left basal opacity , improved from ___ , may represent atelectasis or residual consolidation .