Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Single frontal view of the chest . Sternotomy wires and mediastinal clips are intact . Heart size and cardiomediastinal contours are normal . Lung volumes are low . Vague opacity overlies the left mid lung . No pleural effusion or pneumothorax .
    OUTPUT:
    
Vague opacity overlying the left mid lung may represent pneumonia in the correct clinical context but a mass lesion is not excluded . Follow up PA and lateral radiographs are recommended and consider CT of the chest if the findings do not resolve .