Surgical Pathology Criteria

Usual Interstitial Pneumonia

Differential Diagnosis

Infection must be ruled out in every case

Usual Interstitial Pneumonia Nonspecific Interstitial Pneumonia
Temporal and spatial heterogeneity Temporal and spatial uniformity
Honeycomb change prominent Honeycomb change rare
Scant interstitial inflammation Prominent interstitial inflammation
Prominent fibroblastic foci Fibroblastic foci few, focal


Usual Interstitial Pneumonia Acute Interstitial Pneumonia
Temporal heterogeneity Temporally uniform
Honeycomb change prominent Honeycomb change only in late stage
Patchy distribution with subpleural accentuation Diffuse, uniform throughout
Hyaline membranes not seen Hyaline membranes prominent in early stage


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


Usual Interstitial Pneumonia Desquamative Interstitial Pneumonia
Intra-alveolar macrophages only focally present Diffuse intra-alveolar macrophages
Temporal heterogeneity Temporally uniform
Architecture destroyed, honeycomb change prominent Architecture preserved, honeycomb change uncommon
Fibroblastic foci common Fibroblastic foci absent
Interstitial fibrosis marked Interstitial fibrosis mild to moderate
Interstitial fibrosis variably distributed Interstitial fibrosis tends to be more uniform


Usual Interstitial Pneumonia Cryptogenic Organizing Pneumonia
Temporal heterogeneity Temporally uniform
Honeycomb change prominent Honeycomb change rare
Interstitial fibrosing process Intralumenal fibrosing process
Fibroblastic foci adjacent to mature collagen, covered by epithelium Granulation tissue foci without significant collagen, not subepithelial
Random distribution Bronchiolocentric distribution
Predominantly collagenous fibrosis Predominantly fibroblastic fibrosis
Organizing pneumonia may be seen focally in UIP or in the setting of acute exacerbation of UIP


Usual Interstitial Pneumonia Hypersensitivity Pneumonitis
Lacks granulomas and giant cells Granulomas and giant cells generally present but may be infrequent in late stage
Random distribution Usually has some component of bronchiolocentric distribution even in late stage


Langerhans Cell Histiocytosis Usual Interstitial Pneumonia
Scars frequently stellate and centrilobular with extension to subpleura Irregular subpleural scarring
Honeycomb change only occasionally seen Honeycomb change frequent
Frequently some typical active LCH lesions present Lacks peribronchiolar nodules of Langerhans cells
Langerhans cells are positive for CD1a and langerin CD1a and langerin negative
HRCT shows centrilobular nodule and cyst pattern HRCT shows honeycombing, peripheral accentuation

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