Case 28--Continued


Section 4: Histologic Findings in Mosaic Perfusion of Air-trapping

 

Narrowed Bronchiole

This narrowed bronchiole has some loss of epithelium. The lumen is distorted and contains some exudate. Note the eccentric subepithelial fibrosis and chronic inflammatory cells between the smooth muscle of the airway and the epithelium.

Outline the subepithelial fibrous tissue.

Outline the airway smooth muscle, which is present only around part of the airway.

fibrosismuscle

Obliterated Bronchiole

This bronchiolovascular bundle shows complete obliteration of the airway by fibrous scar. The section is stained with the elastic van Gieson stain. Elastic tissue is black and collagen is red. The elastic layer of the airway is still intact. Without this stain, the airway would appear as a non-specific scar. Its location next to an artery might suggest the diagnosis.

Find the scarred airway.

Find the accompanying artery.

bronchioleartery

Differential diagnosis of mosaic perfusion related to air-trapping on HRCT: Any type of chronic obstructive lung disease including chronic bronchitis/bronchiolitis, bronchiectasis, emphysema, asthma; and also sarcoidosis and hypersensitivity pneumonia

Histologic differential diagnosis of bronchiolitis obliterans: Collagen vascular disease, graft vs host disease in bone marrow transplants, rejection in lung transplants, post-infectious bronchiolitis, toxic fume inhalation, drug reaction. (Note that histologic bronchiolitis obliterans is not seen in airways in emphysema or early asthma.)

Diagnosis: Bronchiolitis obliterans

Diagnostic features of bronchiolitis obliterans on HRCT

Early
Inhomogeneous mosaic perfusion discovered or accentuated on expiratory images
Late
Bronchiectasis

See Case Study 11 for another example of bronchiolitis obliterans. See Case Study 18 for another example of air-trapping with inhomogeneous ground-glass opacity (head cheese pattern).

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Subepithelial fibrosis

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Airway smooth muscle

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Obliterated bronchiole

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Pulmonary artery

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