Table 2.

Scoring system used to grade lesions in H&E-stained lung tissue following infection with SARS-CoV-2.

Parameter	Score	Extent of Lesions
General scores
Gross pathology	0	No macroscopical changes
	1	Focal discoloration of the lung in <15% of lung surface
	2	Multifocal discoloration of approximately 15–40% of lung surface
	3	Multifocal discoloration affecting approximately 40–70% of lung surface
	4	Whole lung affected in >70% of lung surface
Extent lung histopathology (general score, percentage) (H&E)	0	No changes
	1	Focal to multifocal (<15% of tissue)
	2	Multifocal (15–40% of tissue)
	3	Multifocal to coalescing discoloration (40–70% of tissue)
	4	Diffuse (>70% of tissue)
Individual histological parameters (severity)
Alveoli (thickening alveolar wall, type II pneumocyte proliferation, inflammatory cells alveoli)/ interstitial pneumonia	0	No changes
	1	Focal to multifocal (<20% of tissue)
	2	Multifocal (20–50% of tissue)
	3	Multifocal to coalescing (>50% of tissue)
Bronchi and bronchioli	0	No changes
	1	Mild peribronchiolar cuffing and/or infiltrate in lumina without epithelial degeneration <30% of bronchi/bronchioli
	2	Moderate peribronchiolar cuffing and/or infiltrate in lumina without epithelial degeneration >30% of bronchi/bronchioli
	3	Severe peribronchiolar cuffing and/or infiltrate in lumina with epithelial degeneration and necrosis >30% of bronchi/bronchioli
Blood vessels	0	No changes
	1	Perivascular clear spaces (edema) with mild infiltrates of inflammatory cells >30% of large blood vessels
	2	Clear perivascular cuffing in >30% of blood vessels, with minimal vasculitis
	3	Vasculitis in >30% of blood vessels or extensive perivascular cuffing of more than 5 cell layers
Hemorrhage/hemosiderophages (macrophages with hemosiderin)	0	No hemorrhage/hemosiderophages
	1	Mild focal to multifocal hemorrhage/hemosiderophages
	2	Moderate to severe multifocal hemorrhage/hemosiderophages