Macroscopic Findings.
Lungs from all patients were increased in volume, firm, edematous, and congested with diffuse pleural thickening and pleural effusion. Cut surface showed consolidation of lobes and red congested areas, with thickening of the interstitial septa and pulmonary edema (Figure 1A1). Subsegmental pulmonary embolism was seen in 5 cases.
Figure 1.  Pathological findings in lung. A1, Lungs showed an increase in volume and were firmer and heavier than normal. A2 and A3, Light microscopic analysis shows parenchymal multifocal damage with intraalveolar inflammation, fibrin, and hyaline membranes consistent with a diagnosis of diffuse alveolar damage. Both acute exudative inflammatory process and fibrous proliferative phase were found. A3 and A4, Hyperplasia of type II pneumocyte, characterized by amphophilic cytoplasm, large nuclei, and prominent nucleoli, are shown (arrows). B1, Alveolar duct fibrosis. B2, Fibrin thrombi in capillaries. B3, Vascular injury including vessel vasculitis and vascular edema. B4, Pleural fibrosis. Abbreviation: H&E, haematoxylin and eosin. Scale bars: A2, 14 µm; A3–B3, 7 µm; B4, 21 µm.