Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The lungs are well - expanded . Right lung is clear . A heterogeneous retrocardiac opacity is noted . A well demarcated lentiform opacity within the left lower lobe is best seen on frontal view . No pleural effusion or pneumothorax . Heart size , mediastinal contour , and hila are unremarkable .
    OUTPUT:
    
1 . Lentiform opacity projecting over the left lung base is nonspecific and may represent loculated pleural fluid . 2 . Retrocardiac opacity is worrisome for pneumonia .