Histopathological pulmonary findings of survivors and autopsy COVID-19 cases: A bi-center study

The coronavirus disease 2019 (COVID-19), caused by Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2), evolved into a global pandemic. As ACE2 on the surface of alveolar cells of the lung epithelium is one of the potential target receptors for SARS-CoV-2, the respiratory symptoms are the most common presentation of COVID-19. The aim of our study was to investigate the morphological findings in lung tissue after being infected by SARS-CoV-2 and compare histopathologic changes in patients with COVID-19 infection history who died to those who survived. We analyzed lung tissue samples from 9 patients who died from COVID-19 and from 35 patients with COVID-19 infection history who survived and had undergone lung surgery for different reasons. Most of histopathological changes in autopsy and survivors' cases overlapped; however, they occurred with different frequency. The predominant histologic finding both in the case of the deceased and the survivors was patchy distribution of foamy macrophages in the alveolar spaces. In comparison with autopsy cases viral cytopathic-like changes in hyperplastic pneumocytes were rarely observed in the survivors' lung tissue. Pulmonary edema, fibrin deposition within alveoli, bronchopneumonia, small vessel thrombosis and type II pneumocyte hyperplasia were also more often observed within autopsy cases. Life-threatening complications such as hyaline membrane formations and diffuse alveolar damage were present only within the deceased, whereas changes requiring enough time to progress to the fibrotic phase, such as organizing pneumonia, bronchiolization of the alveoli, and interstitial fibrosis were observed in the lung parenchyma only in survivors. Additionally, 14 cases of pulmonary pneumo-hematocele in patients with COVID-19 infection history who survived were observed. It is a newly observed entity in the form of a cystic lesion formed by large accumulation of blood and fibrin between the collapsed and rejected lung parenchyma and/or present with air-fluid levels. The thin wall of pneumo-hematocele is formed by the inter lobar interstitial fibroconnective tissue and has no epithelial lining or bronchial wall elements. As the COVID-19 pandemic continues, new complications following SARS-CoV-2 infection are identified. Newly observed entity in patients with COVID-19 infection history who survived is pulmonary pneumo-hematocele. The appearance of these lesion has become increasingly frequent.