In usual interstitial pneumonia (UIP), the histological pattern that distinguishes it from other forms of ILD is:
- A Uniform temporal and spatial distribution of alveolar inflammation
- B Temporal and spatial heterogeneity with honeycombing, fibroblastic foci, and normal lung in the same biopsy ✓
- C Organising pneumonia (Masson bodies) filling alveolar spaces uniformly
- D Eosinophilic infiltration of alveolar walls with Charcot-Leyden crystals
Correct answer: B. Temporal and spatial heterogeneity with honeycombing, fibroblastic foci, and normal lung in the same biopsy
Explanation
UIP (the histological correlate of IPF) is characterised by temporal and spatial heterogeneity: areas of established honeycombing and fibrosis, acute fibroblastic foci (active fibrosis), and apparently normal lung parenchyma coexist in the same biopsy. This 'patchwork quilt' pattern differentiates it from DIP, NSIP (temporally uniform), or organising pneumonia, and is key to the pathological diagnosis of IPF.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
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