6 Patterns > Acute Lung Injury Pattern > Additional Features

Histologic Features of Specific Causes of Acute Lung Injury

There are 8 specific additional histologic features to search for in the setting of acute lung injury.

Features of Infection

Necrosis
Granulomas
Viral cytopathic effect
Abundant neutrophils

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Features of Connective Tissue Disease

Cellular interstitial infiltrates
Chronic bronchiolitis
Chronic pleuritis
Lymphoid follicle

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Features of Alveolar Hemorrhage

Fresh RBC trapped in fibrin
Hemosiderian laden macrophages
Capillaritis

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Features of Adverse Drug Reaction

Foamy cytoplasm in macrophages and type-II pneumocytes

Fibrosis of Chronic ILD

Dense scarring
Architectural distortion
Microscopic honeycomb remodeling

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Features of Acute Eosinophilic Pneumonia

Eosinophils
Fibrin
Markedly reactive type-II pneumocytes

Sample Signout

If no additional specific histologic features are identified, consider the following approach to signing the case out:

Acute and organizing lung injury (see comment).

Comment: The biopsy shows acute and organizing lung injury without any additional specific histologic features to suggest a definitive etiology. The differential diagnosis includes infection, adverse drug reaction, connective tissue disease, and idiopathic acute lung injury, among a number of other additional possibilities. However, the absence of necrosis, granulomas, neutrophils, and viral cytopathic effect make infection less likely, especially in an immunocompetent patient.

If hyaline membranes are present, consider the following approach to signing the case out:

Acute and organizing diffuse alveolar damage.