Figure 2.

Diffuse alveolar damage is the most consistent finding in the terminal stages of SARS. The lung may appear grossly consolidated (A) or have a honeycomb appearance (B). Although the latter finding may be related to pre‐morbid lung pathology, a correlation with interstitial fibrosis and disease duration has been demonstrated 21. Diffuse alveolar damage at different stages of organization, from fibrin deposition (C, H&E, original magnification ×200), to interstitial fibrosis (D, H&E, original magnification ×100) and cellular organization (E and F, H&E, original magnification ×400), can be detected. Atypical pneumocytes with enlarged nuclei and prominent nucleoli are often seen and some pneumocytes coalesce into syncytial multi‐nucleated cells (G, H&E, original magnification ×600). Multi‐nucleated histiocytes may also be found (H, H&E, original magnification ×600). SARS‐CoV can be detected in pneumocytes by in situ hybridization (I, using a DNA probe against the M gene, original magnification ×600 22). A large array of antibodies against the viral proteins including nucleocapsid N, spike S, membrane M, and SARS‐3a 23, has been developed for the detection of SARS‐CoV in formalin‐fixed, paraffin‐embedded tissue sections (J, showing immunohistochemical staining with an anti‐peptide antibody against N, original magnification ×600)