Diffuse alveolar hemorrhage. (A) The contrast-enhanced thoracic-computer tomography shows widespread patchy ground glass opacification and, in part, a faint “crazy paving” pattern. The contrast between the ground glass areas caused by diffuse alveolar hemorrhage and the air containing bronchi render the bronchi more prominent (dark bronchus sign). There were no signs of pulmonary embolism nor signs of active bronchial artery bleeding. (B) Images of cytological bronchoalveolar lavage specimens. (Upper) Routine Papanicolaou staining shows macrophages (50%-60%) and a significant number of neutrophils, as well as lymphocytes. Almost all macrophages contain a brown-yellow pigment in the cytoplasm. (Lower) Prussian blue staining shows an area with more prominent macrophages, of which most stain intensely blue, denoting iron, reflecting severe intra-alveolar hemorrhage (∼95% of the total macrophage population were hemosiderin-laden macrophages, Golde score 250). Magnification, 40×.