Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Cardiac silhouette size is normal . Mediastinal and hilar contours are unremarkable . Pulmonary vasculature is normal . Focal ill - defined opacity is seen within the left lung base , potentially in the left lower lobe , though not well localized on the lateral view . Right lung is clear . No pleural effusion or pneumothorax is seen . There are no acute osseous abnormalities .
    OUTPUT:
    
Focal ill - defined opacity in the left lung base concerning for pneumonia . Follow up radiographs after treatment are recommended to ensure resolution of this finding .