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
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
Respiratory bronchiolitis associated interstitial lung disease (RBAILD) can be diagnosed only in the presence of clinical disease and in the absence of patterns of other interstitial lung diseases
Acute and nonspecific interstitial lung diseases are diffuse processes and lack the focality of RBAILD
Cryptogenic organizing pneumonia is also bronchiolocentric but is characterized by intralumenal organization, rather than the interstitial fibrosis and intralumenal macrophages of RBAILD
Chronic pulmonary hemorrhage leads to macrophages filled with coarse hemosiderin, not the fine granularity of those in RBAILD
