Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: There is a dense left retrocardiac opacity obscuring the left heart border and left hemidiaphragm . The opacity extends more superiorly in the left upper lobe compared to the prior study of ___ . There is mild atelectasis at the right base . Left mainstem bronchial stent is faintly visualized . Heart size can not be adequately evaluated . There is no large pneumothorax .
    OUTPUT:
    
Mildly worsened dense left retrocardiac opacity obscuring the heart and left hemidiaphragm compatible with known left hilar mass , left lower lobe atelectasis and pleural effusion . Underlying pneumonia can not be excluded .