Fig. 3.

Major histological findings of the lung explant. a Extensive interstitial pulmonary fibrosis with dendriform ossification with the formation of lamellar bone and fatty bone marrow (asterisk). b Higher magnification reveals bronchiolocentric, diffuse interstitial fibrosis with bronchiolar/mucinous and transitional cell metaplasia (yellow arrow) and mucostasis (black asterisk) as well as intra-alveolar and intrabronchiolar desquamation of macrophages (yellow asterisk) and occasional multinucleated giant cells (black arrow). c Accumulation of CD206⁺ (M2-polarized) macrophages in alveolar spaces and the interstitium. d Overexpression of phosphorylated ERK in macrophages but not in alveolar pneumocytes (upper half of the figure). e Increased density of CD105⁺ vessels indicative of neoangiogenesis. Lymphocyte characterization shows a predominance of Tbet⁺ T_H1 cells (f) over GATA3⁺ T_H2 cells (g). h Positivity for N-protein of SARS-CoV-2 in the endothelial lining of an arteriole.