Histopathology patterns and features | |||||
UIP | Probable UIP | Indeterminate for UIP | Alternative diagnosis | ||
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Idiopathic pulmonary fibrosis (IPF) diagnosis on the basis of high-resolution computed tomography (HRCT) and biopsy patterns, developed using consensus by discussion | |||||
IPF suspectedΔ | Histopathology pattern◊ | ||||
UIP | Probable UIP | Indeterminate for UIP or biopsy not performed | Alternative diagnosis | ||
HRCT pattern | UIP | IPF | IPF | IPF | Non-IPF diagnosis |
Probable UIP | IPF | IPF | IPF (likely)§ | Non-IPF diagnosis | |
Indeterminate | IPF | IPF (likely)§ | Indeterminate¥ | Non-IPF diagnosis | |
Alternative diagnosis | IPF (likely)§ | Indeterminate¥ | Non-IPF diagnosis | Non-IPF diagnosis |
IPF: idiopathic pulmonary fibrosis; UIP: usual interstitial pneumonia; IIP: idiopathic interstitial pneumonia; LAM: lymphangioleiomyomatosis; HRCT: high resolution computed tomography.
* Granulomas, hyaline membranes (other than when associated with acute exacerbation of IPF, which may be the presenting manifestation in some patients), prominent airway-centered changes, areas of interstitial inflammation lacking associated fibrosis, marked chronic fibrous pleuritis, organizing pneumonia. Such features may not be overt or easily seen to the untrained eye and often need to be specifically sought.
¶ Features that should raise concerns about the likelihood of an alternative diagnosis include a cellular inflammatory infiltrate away from areas of honeycombing, prominent lymphoid hyperplasia including secondary germinal centers, and a distinctly bronchiolocentric distribution that could include extensive peribronchiolar metaplasia.
Δ "Clinically suspected of having IPF" is defined as unexplained patterns of bilateral pulmonary fibrosis on chest radiography or chest computed tomography, bibasilar inspiratory crackles, and age >60 years. Middle-aged adults (>40 and <60 years old) can rarely present with otherwise similar clinical features, especially in patients with features suggesting familial pulmonary fibrosis.
◊ Diagnostic confidence may need to be downgraded if histopathological assessment is based on transbronchial lung cryobiopsy given the smaller biopsy size and greater potential for sampling error compared with surgical lung biopsy.
§ IPF is the likely diagnosis when any of the following features are present:¥ Indeterminate for IPF:
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