Pathology for COVID-19 Infectious Diseases



PDF - PATHOLOGY from Infectious Diseases Team

Review key facts, bulleted text, essential images and current references.

PATHOLOGY from Infectious Diseases Team

COVID-19 Infectious Diseases by Isaac Solomon, MD, PhD

Severe Acute Respiratory Syndrome Coronavirus 2

This illustration of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) shows surface spikes (red), giving a halo appearance incorporated into the name "corona." (Courtesy A. Eckert, MS and D. Higgins, MAMS.)

Ultrastructural Features

This transmission electron micrograph shows spherical extracellular particles with surface spikes and cross sections through the viral genome (black dots), features characteristic of SARS-CoV-2. (Courtesy C. Goldsmith, CDC and A. Tamin, CDC.)

Chest X-Ray

This portable chest X-ray shows parenchymal opacities with asymmetric distribution, consolidation in the right perihilar region, and opacity in left lung base, findings consistent with COVID-19 pneumonia.

Histopathologic Features

This autopsy lung section shows hyaline membranes, interstitial edema and inflammation, and squamous metaplasia, features consistent with diffuse alveolar damage. Confirmation of SARS-CoV-2 infection requires IHC, ISH, or PCR. (Courtesy R. Padera, Jr., MD, PhD.)

Gross Features

This section of lung from a fatal case of COVID-19 shows areas of red congested and edematous parenchyma, consistent with diffuse alveolar damage. (Courtesy R. Padera, Jr., MD, PhD.)

Hyaline Membranes

Early histologic findings in COVID-19 pneumonia include eosinophilic hyaline membranes consistent with exudative (acute) diffuse alveolar damage. (Courtesy R. Padera, Jr., MD, PhD.)

Interstitial Inflammation and Edema

COVID-19 pneumonia includes variable amounts of interstitial and perivascular chronic inflammation and edema. (Courtesy R. Padera, Jr., MD, PhD.)

Fibrin Thrombi

Fibrin thrombi involving small vessels are occasionally present in COVID-19 pneumonia. (Courtesy R. Padera, Jr., MD, PhD.)

Squamous Metaplasia

Squamous metaplasia is frequently present in the lungs in COVID-19 pneumonia, and can exhibit significant cytologic atypia. (Courtesy R. Padera, Jr., MD, PhD.)

Multinucleated Giant Cells

Multinucleated giant cells with prominent reactive-appearing nucleoli are variably present in COVID-19 pneumonia. (Courtesy R. Padera, Jr., MD, PhD.)

Cytoplasmic Inclusions

Multinucleated giant cells may contain basophilic cytoplasmic inclusions of unclear etiology. (Courtesy R. Padera, Jr., MD, PhD.)


A reactive histiocyte is present containing an engulfed lymphocyte that should not be confused with a viral inclusion. (Courtesy R. Padera, Jr., MD, PhD.)

Proliferative (Organizing) Phase

Later changes in COVID-19 pneumonia include proliferation of pneumocytes and fibroblasts to form loose organizing connective tissue. (Courtesy R. Padera, Jr., MD, PhD.)

Fibroblast Proliferation

Fibroblast proliferation and collagen production in alveolar spaces reflects organized alveolar damage. (Courtesy R. Padera, Jr., MD, PhD.)

Large Airway Involvement

Large airways in COVID-19 occasionally show lymphocytic bronchitis/bronchiolitis with reactive epithelial changes and occasional intraepithelial neutrophils. (Courtesy R. Padera, Jr., MD, PhD.)

Bacterial Bronchopneumonia

Coinfections with bacteria, fungi, and other respiratory viruses are common with COVID-19. This section shows multiple collections of basophilic bacteria embedded in intraalveolar neutrophils. (Courtesy R. Padera, Jr., MD, PhD.)

Chest CT

This chest CT from a patient positive for COVID-19 shows bilateral upper and lower lobe peribronchial ground-glass and consolidative opacities.

RT-PCR Testing

RT-PCR of respiratory specimens is the most common test used for confirmation of COVID-19. (Courtesy CDC.)

SARS Histopathology

Section of a lung in a patient with SARS shows diffuse alveolar damage and a multinucleated giant cell with no conspicuous viral inclusions , findings similar to those reported in COVID-19. (Courtesy S. Zaki, MD, PhD.)