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. 2022 Mar;192(3):454–467. doi: 10.1016/j.ajpath.2021.11.014

Figure 3.

Figure 3

Absence of fibrosis in early coronavirus disease 2019 (COVID-19) acute respiratory distress syndrome. A: Trichrome highlighted (in blue) basement membranes and vascular adventitia in normal and COVID-19 lungs and collagen deposition with marked fibrosis in idiopathic pulmonary fibrosis (IPF). B: Immunostaining revealed abundant myofibroblasts in IPF but not in COVID-19. Open arrowheads indicate smooth muscle cells; closed arrowheads indicate myofibroblasts. C: Serial sections were stained for hematoxylin and eosin (H&E) (left panel) or KRT8 (right panel). Transitional cells (black and white arrowheads) overlie fibroblastic focus (black and white asterisks). n = 3. Scale bars = 50 μm. α-SMA, α-smooth muscle actin.