Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The heart is of normal size with normal cardiomediastinal contours . Left perihilar opacity is again seen , compatible with known mass and parenchymal scarring as seen on ___ CT . A small left pleural effusion is present . No pneumothorax . Leads of a left chest wall pacer terminate in the right atrium and right ventricle . The osseous structures are unremarkable .
    OUTPUT:
    
No appreciable change since ___ , allowing for difference in modality . Left perihilar opacity , compatible with known mass and scarring . Small left pleural effusion .