Surgical Pathology Criteria

Respiratory Bronchiolitis Associated Interstitial Lung Disease

Differential Diagnosis

Respiratory Bronchiolitis Associated Interstitial Lung Disease Usual Interstitial Pneumonia
Fibrosis does not destroy architecture, no honeycombing Fibrosis destroys architecture, honeycombing is prominent
No fibroblastic foci Frequent fibroblastic foci
Air spaces filled with macrophages Filling of airspaces with macrophages is not seen
HRCT shows centrilobular nodule pattern HRCT shows honeycombing, peripheral accentuation

 

Respiratory Bronchiolitis Associated Interstitial Lung Disease Desquamative Interstitial Pneumonia
Patchy Diffuse pulmonary involvement
Intra-alveolar macrophages only focally present Diffuse intra-alveolar macrophages
Mild pneumocyte hyperplasia Prominent pneumocyte hyperplasia
Peribronchiolar thickening Interstitial thickening

 

Respiratory Bronchiolitis Associated Interstitial Lung Disease Langerhans Cell Histiocytosis
Predominantly intra-alveolar process Predominantly interstitial process, intra-alveolar macrophages only focally present
Eosinophils rare Eosinophils may be numerous
No cystic change Cystic change frequent
Lacks scarring Produces stellate scars
Histiocytes with round nuclei Histiocytes with folded nuclei
Macrophages CD1a and langerin negative Langerhans cells positive for CD1a and langerin
Both are highly associated with smoking, thus foci or respiratory bronchiolitis are expected to be present in the lung tissue of cases of Langerhans cell histiocytosis

 

Respiratory Bronchiolitis Associated Interstitial Lung Disease Hypersensitivity Pneumonitis
Lacks granulomas and giant cells Granulomas and giant cells generally present but may be infrequent in late stage
Smoking history only Possible exposure history
May develop mild-moderate peri-bronchiolar fibrosis but architecture is preserved May develop significant fibrosis with honeycomb change

 

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