Usual interstitial pneumonia (UIP) is the histological pattern of idiopathic pulmonary fibrosis (IPF). The diagnostic hallmark on lung biopsy is:
- A Uniform diffuse interstitial fibrosis without honeycombing (NSIP-like pattern)
- B Temporal heterogeneity — areas of old fibrosis with honeycombing adjacent to areas of active fibroblast foci in normal lung — in a subpleural, basal distribution ✓
- C Granulomas with giant cells and areas of organizing pneumonia
- D Dense eosinophilic infiltrates with patchy airspace organization
Correct answer: B. Temporal heterogeneity — areas of old fibrosis with honeycombing adjacent to areas of active fibroblast foci in normal lung — in a subpleural, basal distribution
Explanation
UIP pattern is characterized by temporal and spatial heterogeneity — a patchwork of dense fibrosis with honeycomb change (subpleural, basal predominance) immediately adjacent to relatively normal or minimally affected lung, with fibroblast foci (aggregates of active fibroblasts at the advancing edge of fibrosis). This is distinct from NSIP (temporally uniform fibrosis) and hypersensitivity pneumonitis (granulomas, peribronchiolar distribution). The fibroblast foci represent the active injury front where TGF-β drives fibroblast-to-myofibroblast transition.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.