Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Frontal and lateral chest radiographs were obtained . Mild atelectasis is noted at the left lung base . No focal opacity is identified . The cardiomediastinal silhouette , hilar contours , and pleural surfaces are normal . There is no pleural effusion or pneumothorax . Known left mid lung granuloma is unchanged .
    OUTPUT:
    
Left lung base atelectasis , no focal opacity identified .