Surgical Pathology Criteria

Cryptogenic Organizing Pneumonia - Bronchiolitis Obliterans Organizing Pneumonia

Differential Diagnosis

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


Cryptogenic Organizing Pneumonia Acute Interstitial Pneumonia
Patchy distribution Diffuse
No hyaline membranes Hyaline membranes prominent in early stage and fragments in organizing phase
No collagen deposition, architecture preserved Diffuse honeycomb change may be seen in late stage


Cryptogenic Organizing Pneumonia (BOOP) Acute Eosinophilic Pneumonia
Subacute onset Acute, fulminant onset
Eosinophils infrequent Prominent eosinophils in lavage and biopsy specimens
BOOP pattern may be seen in acute eosinophilic pneumonia


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