COVID-19-Associated Acute Respiratory Distress Syndrome: Lessons from Tissues and Cells.

Reports examining lung histopathology in coronavirus disease 2019 (COVID-19) infection provide an essential body of information for clinicians and investigators. Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2)-induced lung injury is complex, involving the airways, alveoli, and pulmonary vessels. Although no anatomic marker is specific, the signature histologic lesion is diffuse alveolar damage (DAD). The biological and molecular mechanisms that drive this pattern of injury are unknown, and the relationship of SARS-CoV-2-induced DAD to physiologic alterations and clinical outcomes in COVID-19-associated acute respiratory distress syndrome is undefined. Additional histologic patterns that may be variant phenotypes have been reported.