A 45-year-old patient with progressive dyspnea has a chest CT showing bilateral ground-glass opacities and honeycombing in the lower lobes. Surgical lung biopsy shows dense fibrosis with architectural distortion, fibroblastic foci at the advancing fibrotic front, and relative sparing of the upper lobes. The histological pattern is:

• A Usual interstitial pneumonia (UIP) ✓
• B Non-specific interstitial pneumonia (NSIP)
• C Organizing pneumonia (OP/BOOP)
• D Desquamative interstitial pneumonia (DIP)

Explanation

The UIP (Usual Interstitial Pneumonia) pattern is the histological hallmark of idiopathic pulmonary fibrosis (IPF). Key features: temporal and spatial heterogeneity (areas of honeycombing adjacent to normal lung), subpleural and basal predominance, fibroblastic foci at the active fibrotic edge, and dense collagenous fibrosis with cystic change (honeycombing). NSIP shows diffuse, temporally uniform fibrosis without honeycombing or fibroblastic foci. OP shows intraluminal fibroblastic plugs in airspaces. DIP shows diffuse alveolar macrophage accumulation.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

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Written and medically reviewed by the StethoPrep medical team.