Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The right lung is well expanded and there is an elevated left hemidiaphragm , similar prior exam . There is a 4 .5 cm mass in the left upper lung , slightly increased in size from prior and consistent with known history of lung cancer . Diffuse interstitial markings which could represent chronic interstitial disease , lymphatic spread of tumor , or mild pulmonary edema . An opacity is seen at the left lung base , likely representing atelectasis although can not exclude pneumonia or aspiration in the right clinical setting . Elevation of left hemidiaphragm makes evaluation of the cardiac silhouette difficult , but the heart is likely somewhat enlarged .
    OUTPUT:
    
1 . Opacity at the left lung base , likely representing atelectasis but can not exclude pneumonia or aspiration in the right clinical setting . 2 . 4 .5 cm mass in the left upper lung , slightly increased in size from prior and consistent with known history of lung cancer . 3 . Diffuse interstitial markings which could represent chronic interstitial disease , lymphatic spread of tumor , or mild pulmonary edema . .