Usual Interstitial Pneumonia (UIP)
Idiopathic Pulmonary Fibrosis (IPF)
Cryptogenic Fibrosing Alveolitis
Epidemiology:
Common sites:
Gross features:
- cobblestoned pleural surface (retraction of
scars along interlobular septa)
- fibrosis on cut section
- firm, rubbery, white areas
- lower-lobe predominant
- subpleural regions and along interlobular septa
Histologic features:
- alveolitis
(early nonspecific finding)
- inflammation within the alveolar walls and
spaces
- patchy interstitial fibrosis (hallmark)
- subpleural, paraseptal, and occasional peribronchovascular accentuation
- coexistence of early and late lesions and
normal lung is typical (temporal heterogeneity)
- fibroblastic foci (characteristic, early
lesions)
- exhuberant fibroblastic proliferation
- fibres running parallel to surface
- bluish myxoid
extracellular matrix
- typically at edge of areas of dense fibrosis
- over time they become more collagenous and less
cellular
- honeycomb fibrosis (late stage lesion):
- collapse of alveolar walls and formation of
cystic spaces lined by hyperplastic type II pneumocytes
or bronchiolar epithelium (metaplastic)
- smooth muscle metaplasia
- mild to moderate inflammation in fibrotic areas:
- lymphocytes mostly
- plasma cells
- neutrophils
- eosinophils
- mast cells
- pulmonary hypertensive changes in pulmonary
arteries
- intimal fibrosis
- medial thickening
- squamous metaplastic
foci maybe
- smooth muscle hyperplasia maybe
- NB. May have acute exacerbations manifested by
DAD / AFOP pattern
Immunophenotype:
Marker:
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Sensitivity:
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Specificity:
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Molecular features:
Other features:
- UIP is the histologic description, which is
nonspecific
- IPF is the clinicopathologic
syndrome
- TH2-type inflammatory response in IPF
- Clinical features:
- Gradual deterioration despite treatment
- Increased risk for cancer
References: