Table 3.

Summary of Histologic Findings

Patients	Airway	Alveoli	Interstitium	Vessel
Negative control patients
1	Unremarkable	Emphysema, pigmented macrophages, focal organizing pneumonia	Mild interstitial fibrosis, carcinoid (micro)tumorlet	PH
2	Basement membrane fibrosis/small airway disease	Mild emphysema, bronchiolar metaplasia	Anthracosis, focal lymphoid aggregates, focal mild fibrosis	Unremarkable
3	Goblet cell hyperplasia	Emphysema, rare giant cells	Anthracosis	PH
4	Basement membrane fibrosis	Mild emphysema, edema, rare poorly formed granulomas with giant cells	Variably fibrotic with some severely fibrotic areas, foci of interstitial lymphoid infiltrate, anthracosis	PH, granuloma in vessel wall
5	Unremarkable	Mild emphysema	Anthracosis	Unremarkable
COVID-19 survivors
6	Unremarkable	Emphysema, atypical adenomatous hyperplasia, rare pigmented macrophages	Anthracosis	Unremarkable
7a	Respiratory bronchiolitis	Emphysema, pigmented macrophages, Langerhans cell histiocytosis	Smoking-related interstitial fibrosis, scattered lymphoid aggregates	Unremarkable
7b	Respiratory bronchiolitis, peribronchiolar fibrosis	Emphysema, pigmented macrophages, focal edema	Smoking-related interstitial fibrosis	Unremarkable
8	Mild peribronchiolar inflammation	Emphysema, focal poorly formed granulomas	Mild interstitial thickening, perivascular lymphoid aggregates	Unremarkable
9	Peribronchiolar fibrosis	Emphysema, with patchy chronic inflammation, focal edema	Patchy widened, smoking-related interstitial fibrosis	PH
10	Unremarkable	Mild emphysema	Mild interstitial fibrosis, anthracosis	PH
11	Basement membrane fibrosis	Emphysema, rare foamy macrophages	Rare foci of fibrosis, anthracosis	PH
12	Basement membrane fibrosis/small airway disease	Scattered poorly-formed granulomas and mild patchy inflammation	Poorly formed granulomas, anthracosis	PH
13	Mild small airway disease	Emphysema, scattered foamy macrophages	Unremarkable	PH
14	Unremarkable	Emphysema	Congestion, focal lymphoid infiltrate	Unremarkable
15	Peribronchial inflammation and fibrosis	Emphysema, rare organizing pneumonia	Mild interstitial inflammation, patchy fibrosis	Unremarkable
16	Unremarkable	Mild emphysema, edema, focal fibrin	Unremarkable	Unremarkable
COVID-19 end-stage lung disease
17	Submucosal lymphohistiocytic infiltrate	Intra-alveolar macrophages, collapse	Diffuse fibrosis (fibrotic DAD), focal changes suggestive of interstitial emphysema, patchy chronic inflammation, calcifications	Recanalized thrombi
18	Basement membrane fibrosis, submucosal lymphohistiocytic and eosinophilic inflammation, intraepithelial neutrophils suggestive of superimposed infection	Organizing pneumonia, collapse, abundant hemosiderin-laden macrophages, microcystic change with bronchiolar squamous metaplasia	Diffuse fibrosis (fibrotic DAD), moderate lymphocytic/mononuclear inflammation, pulmonary interstitial emphysema	Large recanalized thrombus
19	Postmortem sloughing of epithelium, submucosal edema, mild lymphocytic inflammation	Diffuse alveolar damage, mild hemorrhage, reactive pneumocytes	Mild but diffuse interstitial lymphocytic inflammation, edema	Focal perivascular edema

DAD, diffuse alveolar damage; PH, pulmonary hypertension.