Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: There is asymmetry of the right lung base , which could be merely atelectasis , but given the clinical history , the possibility of superimposed pneumonia is considered . The right hilum is more prominent than the left , although this has not much changed since the radiograph from ___ years prior in ___ . There is no pleural effusion or pneumothorax . Osseous structures are unremarkable .
    OUTPUT:
    
1 . Asymmetry of the right lung base could be merely atelectasis , however given the clinical history , a superimposed pneumonia is considered .