Figure 4a. Respiratory bronchiolitis-associated interstitial lung disease in a 30-year-old woman. (a) High-resolution CT scan of the upper lobe demonstrates centrilobular ground-glass attenuation (arrows). (b) Photomicrograph (original magnification, x40; hematoxylin-eosin stain) shows a terminal bronchiole filled with pigmented macrophages (a). (c) Photomicrograph (original magnification, x50; hematoxylin-eosin stain) shows the "tobacco pigment" in macrophages (a) within alveolar ducts and alveoli. Collagenous scarring involves interstitium between alveoli. b = mild bronchiolar fibrosis, c = chronic inflammation.