A 55-year-old non-smoker woman presents with progressive dyspnea. HRCT shows bilateral basal predominant honeycombing with traction bronchiectasis but no ground-glass opacity. Surgical lung biopsy shows spatial and temporal heterogeneity with fibroblast foci, honeycombing, normal lung, and fibrosis alternating — predominantly subpleural and basal. This histological pattern is:
- A Non-specific interstitial pneumonia (NSIP) — ground-glass and reticulation, temporal homogeneity, responds to steroids
- B Cryptogenic organizing pneumonia (COP) — filling of alveolar spaces with Masson's bodies; steroid-responsive
- C Usual interstitial pneumonia (UIP) — temporal and spatial heterogeneity with fibroblast foci; correlates with IPF diagnosis ✓
- D Acute interstitial pneumonia (AIP) — diffuse alveolar damage pattern; rapidly progressive
Explanation
Usual interstitial pneumonia (UIP) is the histological pattern in idiopathic pulmonary fibrosis (IPF) and is defined by: temporal heterogeneity (old fibrosis + acute fibroblast foci), spatial heterogeneity (fibrosis alternating with normal lung), subpleural and basal predominance, and honeycomb change ± traction bronchiectasis. Fibroblast foci represent the leading edge of fibrogenesis and are pathognomonic of UIP. When UIP pattern is seen on HRCT without a secondary cause, IPF diagnosis is made (ATS/ERS guidelines 2022). NSIP shows temporal homogeneity; COP shows Masson bodies; AIP shows hyaline membranes.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
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Written and medically reviewed by the StethoPrep medical team.