Evidence of marked fibrosis/architectural distortion±honeycombing in a predominantly subpleural/paraseptal distribution | Evidence of marked fibrosis/architectural distortion±honeycombing | Patchy or diffuse involvement of lung parenchyma by fibrosis, with or without interstitial inflammation | Hyaline membranes§ |
Presence of patchy involvement of lung parenchyma by fibrosis | Absence of either patchy involvement or fibroblastic foci, but not both | Absence of other criteria for UIP (see first column) | Organising pneumonia§,ƒ |
Presence of fibroblast foci | Absence of features against a diagnosis of UIP suggesting an alternative diagnosis (see fourth column) OR Honeycomb changes only## | Absence of features against a diagnosis of UIP suggesting an alternative diagnosis (see fourth column) | Granulomasƒ |
Absence of features against a diagnosis of UIP suggesting an alternative diagnosis (see fourth column) | | | Marked interstitial inflammatory cell infiltrate away from honeycombing |
| | | Predominant airway centred changes |
| | | Other features suggestive of an alternative diagnosis |