Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The heart is normal in size . The mediastinal and hilar contours appear within normal limits . There is no pleural effusion or pneumothorax . There is a substantial nodular opacity projecting along the left lower lung which may be associated with a nipple shadow or confluence of soft tissue or even potentially atelectasis but when clinically appropriate evaluation with a chest CT is recommended in order to exclude a true lung nodule . Otherwise the lungs appear clear . The osseous structures are unremarkable .
    OUTPUT:
    
1 . No evidence of acute disease . 2 . Nodular opacity in the left lower lung , possibly an artifact or focus of atelectasis , but when clinically appropriate chest CT follow - up is recommended to evaluate further .