Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Single AP view of the chest . There is dense opacity in the right upper lobe , particularly laterally . Given differences in technique , this is not significantly changed since PET - CT scan from 3 days prior . Increased density projecting over the right hemithorax from compared to the left is compatible with a layering effusion . Left lung is clear . Cardiomediastinal silhouette is unchanged . No acute osseous abnormality is detected .
    OUTPUT:
    
No significant interval change . Persistent opacity in the right upper lobe likely in part due to central obstructing perihilar mass better characterized by prior cross - sectional imaging . No definite superimposed acute process .