Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Smooth left focal pleural thickening measures 2 .5 cm in width and 9 .5 cm in height is unchanged in appearance since ___ . Lucent areas with in the pleural thickening probably represent air . The lung parecnhyma adjacent to the lesion is abnormal which may be due to adjacent atelectasis or scarring . There is a small left pleural effusion . The cardiac and mediastinal contours are normal .
    OUTPUT:
    
Left focal pleural thickening and adjacent abnormal lung , unchanged since ___ . The etiology is uncertain , but presumably chronic . The differential diagnosis includes empyema from prior tuberculosis or other infection and chronic hematoma from prior trauma , however , superimposed acute infection can not be excluded . After discussion with Dr . ___ ___ the 6 month stability of the pleural thickening and the patient 's knowledge of this finding , it was decided that no further workup was indicated at this time .