(A) Gross pathology of caseonecrotic pneumonia; cut surfaces of lung tissue with various sized caseonecrotic lesions (largest area depicted by asterisk). There is marked interlobular fibrosis and suppurative bronchopneumonia in the remaining lung parenchyma. Calf no. 5. Bar = 1 cm; (B) Histopathology of caseonecrotic pneumonia; caseonecrotic lung lesion. The eosinophilic centre (N) is demarcated by inflammatory cells and remnants of necrotic bronchiolar epithelium (arrows). Calf No. 3. H&E. Bar = 184 μm; (C) Immunohistochemical detection of wide spectrum cytokeratin-positive epithelial cells; immunohistochemical staining with antibodies (mAb AE1/AE3) to wide spectrum cytokeratin of the same bronchiole as shown in (B) reveals remnants of bronchiolar epithelial cells (arrows) surrounding the necrotic area (N). At the periphery, demarcating macrophages are present (asterisk). Calf No. 3. ABC method. Bar = 92 μm; (D) Histopathology of obliterative bronchiolitis; obliterative bronchiolitis with vacuolated epithelial cells (arrows) and intraluminal fibroblasts and inflammatory cells. Calf No. 5. H&E. Bar = 46 μm.