Figure 3b. Postprimary active tuberculosis in a 34-year-old man with weight loss and a chronic cough. (a) High-resolution CT scan of the left lung shows a thick-walled cavity and multiple peripheral small nodules and branching linear structures (arrows). Note the thickening of the bronchial walls (arrowhead). (b) Photomicrograph (original magnification, x400; hematoxylin-eosin stain) shows impacted caseous material (*) in small peripheral airways (arrow).