Parameters:
(1) fibrosis and architectural disortion
(2) distribution
(3) patchy involvement of lung parenchyma by fibrosis
(4) fibroblastic foci
(5) features suggesting an alternative diagnosis
(6) acute exacerbation
Features suggesting another diagnosis (not UIP):
(1) marked interstitial inflammatory cell infiltrate away from honeycombing
(2) changes predominantly airway centered
(3) histopathologic features suggesting another diagnosis
(4) hyaline membranes AND not acute exacerbation
(5) organizing pneumonia AND not acute exacerbation
(6) granulomas AND not isolated or occasional
Features indicating UIP – all of the following:
(1) evidence of marked fibrosis and architectural distortion with or without honeycombing
(2) predominantly subpleural and/or paraseptal distribution
(3) patchy involvement of lung parenchyma by fibrosis
(4) presence of fibroblastic foci
(5) no features suggesting another diagnosis
Features indicating probable UIP – all of the following:
(1) evidence of marked fibrosis and architectural distortion with or without honeycombing
(2) one of the following:
(2a) patchy involvement of lung parenchyma by fibrosis
(2b) presence of fibroblastic foci
(3) one of the following:
(3a) no features suggesting another diagnosis
(3b) honeycombing changes only (avoid by identifying a biopsy site on high-resolution CT scan prior to surgery)
Features indicating possible UIP – all of the following:
(1) patchy involvement of lung parenchyma by fibrosis with or without interstitial inflammation
(2) other findings of UIP absent
(3) no features suggesting another diagnosis
