Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The cardiomediastinal contours are normal . Prominence of the left main pulmonary artery is noted . There is no pleural effusion or pneumothorax . There is a rounded ill - defined retrocardiac nodule , only seen on the lateral view without a clear correlate on the frontal view .
    OUTPUT:
    
1 . Retrocardiac opacity only seen on the lateral view . If infectious symptoms are present , this may be treated , and a followup chest radiograph is recommended to document resolution . In the absence of infectious symptoms , CT is recommended for further evaluation . 2 . Enlarged left main pulmonary artery , which may also be assessed further with chest CT if clinically indicated . Dr . ___ ___ these items into the Critical Results Dashboard on ___ .