Usual interstitial pneumonia (American thoracic society criteria for histopathological diagnosis)
American Thoracic Society (ATS) criteria for the histopathological diagnosis of usual interstitial pneumonia (UIP) are as follows:
- advanced subpleural or paraseptal fibrosis +/- honeycombing
- patchy temporally heterogeneous fibrosis
- fibroblastic foci
- the absence of features against UIP
- inflammatory cells
- granulomas
- organizing pneumonia
The most important difference is that presence of honeycombing is not a major criterion for the diagnosis of UIP in pathology as opposed to chest HRCT, although in the majority of cases microscopic fibrotic cysts can be seen which could be considered precursors of the macroscopic subpleural honeycombing on HRCT chest.
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