Pathology for COVID-19 SARS Pneumonia



PDF - PATHOLOGY from Thoracic Team

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

PATHOLOGY from Thoracic Team

SARS Pneumonia by Mari Mino-Kenudson, MD; David I. Suster, MD; and Saul Suster, MD

CT Scan of Advanced-Stage COVID-19

A representative CT scan of advanced-stage COVID-19 demonstrates numerous foci of ground-glass opacity with multifocal consolidations. (Courtesy Dr. Brent Little.)

Gross Image of COVID-19 Lung3

A parasagittal section of the lung from a COVID-19 autopsy shows multifocal consolidations consistent with an advanced stage of the disease +/- superimposed bronchopneumonia. (Courtesy of Dr. Isaac Solomon and Robert Padera.)

Edema and Congestion

An early-phase image of COVID-19 shows extensive areas of edema and congestion with increased cellularity of alveolar walls but no hyaline membranes (magnification 200x). Of note, inflammatory infiltrate may be limited to perivascular areas in the early phase.

Exudative Phase of DAD

(LEFT) A representative section from a COVID-19 autopsy demonstrates the architecturally intact lung parenchyma diffusely involved by hyaline membrane formation consistent with the exudative phase of DAD (magnification 20x). (RIGHT) Higher-power magnification shows multiple alveoli lined by thick hyaline membranes, a feature commonly seen in fulminant cases of SARS or COVID-19 (magnification 100x).

Early Organizing Phase of DAD

In this autopsy from a COVID-19 patient, there are scattered foci with a spindle cell proliferation , leading to mild thickening of alveolar walls along with prominent hyaline membranes, consistent with the early organizing phase of DAD (magnification 400x).

Multinucleated Giant Cells

Scattered, usually rare, multinucleated giant cells may be seen throughout the lung parenchyma in cases of SARS or COVID-19. Of note, prominent intracytoplasmic inclusions are not a feature of SARS.

Viral Cytopathic Changes

Viral cytopathic changes are rarely seen in COVID-19 lungs. This rare example shows an intracytoplasmic inclusion in a detached cluster of enlarged type II pneumocytes, suggestive of viral cytopathic changes (magnification 600x).

Proliferative Phase of DAD

The proliferative phase of DAD is characterized by marked alveolar wall thickening and collapse of alveoli, resulting in scattered large airspaces in the "consolidative"-appearing background (magnification 20x).

Organizing Pneumonia - Pattern of Fibrosis

(LEFT) Areas with an organizing pneumonia pattern may be seen and characterized by fibromyxoid proliferation with scattered inflammatory cells filling alveolar spaces (magnification 100x). (MIDDLE) Elastic stain highlights intact alveolar framework (black lines) in the background of the fibromyxoid proliferation filling alveolar spaces (magnification 100x). (RIGHT) Trichrome stain reveals a lack of mature collagen in the intraalveolar fibromyxoid proliferation consistent with organizing fibrosis. Of note, alveolar walls show mild mature collagen fibrosis highlighted blue in this case (magnification 100x).

Vascular Damage

SARS may show focal areas of vascular damage in which inflammatory infiltrates infiltrate vessel walls (magnification 200x).

Fibrin Thrombus

COVID-19 lungs may have a large number of fibrin thrombi in small pulmonary arteries, beyond the range seen in conventional DAD, reflecting a hypercoagulable state (magnification 100x).

RNA In Situ Hybridization for COVID-19

RNA in situ hybridization for COVID-19 demonstrates high viral RNA copy number within type II pneumocytes (magnification 200x). (Courtesy Dr. Gerard Nuovo.)

SARS Nucleocapsid Immunostain

SARS nucleocapsid immunostain highlights type II pneumocytes in an autopsy section from a patient with COVID-19 (magnification 600x).

Complement-Associated Microvascular Injury

(LEFT) A small subset of COVID-19 patients exhibit septal capillary injury with significant mural and luminal fibrin deposition in capillaries and permeation of the inter-alveolar septa by neutrophils. Features of classic DAD are not present (magnification 200x). (Courtesy Drs. Cynthia Magro and J. Justin Mulvey.) (MIDDLE) Septal capillary injury is characterized by capillary wall disruption accompanied by fibrin deposition and red cell extravasation (magnification 1,000x). (Courtesy Drs. Cynthia Magro and J. Justin Mulvey.) (RIGHT) Extensive C4d deposition is seen throughout the lung parenchyma, with striking septal capillary localization (magnification 200x). (Courtesy Drs. Cynthia Magro and J. Justin Mulvey.)

Colocalization of Complement Components with SARS-CoV2

Merged immunofluorescence of C4d (green) and SARS-CoV2 spike glycoprotein (red) reveals a significant degree of C4d and SARS-CoV2 colocalization (yellow) within the alveolar septa, suggestive of activation of complement pathways with SARS-CoV2 spike glycoprotein. (Courtesy Drs. Cynthia Magro and J. Justin Mulvey.)