Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Heart size is normal . The mediastinal and hilar contours are normal . The pulmonary vasculature is normal . Lungs demonstrate interval slight progression of a bilateral reticular pattern of chronic interstitial fibrotic lung disease with a subpleural and basilar predominance . No pleural effusion or pneumothorax is seen . There are no acute osseous abnormalities .
    OUTPUT:
    
Slow progression of diffuse interstitial lung disease , likely a fibrotic subtype of NSIP . No definite superimposed pneumonia , but subtle infectious abnormalities may be difficult to detect in the setting of diffuse lung disease .