Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Subtle opacity projecting over the left lung base on the frontal view , not substantiated on the lateral view , most likely represents atelectasis , early infection is not excluded in the appropriate clinical setting . The right lung is clear . No pleural effusion or pneumothorax is seen . Cardiac and mediastinal silhouettes are unremarkable .
    OUTPUT:
    
Subtle opacity projecting of the left lung base on the frontal view , not substantiated on the lateral view , most likely represents atelectasis , early infection not excluded in the appropriate clinical setting .