Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: There is persistent , perhaps somewhat increased opacification in the posterior left lower lobe indicating atelectasis superimposed on a large rounded mass in the left posterior costophrenic sulcus which is similar in size although hard to compare to the prior CT for small possible changes . Elsewhere , the lungs remain clear . Additional known nodules are not well seen on radiography for the most part . There is no definite pleural effusion .
    OUTPUT:
    
Mild increase in opacification in the left lower lobe , probably associated with atelectasis in the vicinity of a large known metastasis .