A 55-year-old man who never smoked presents with lower lobe-predominant ground-glass opacities and honeycombing on HRCT. Lung biopsy shows temporal and spatial heterogeneity with fibroblastic foci, dense fibrosis, and honeycombing adjacent to areas of normal lung — a pattern described as usual interstitial pneumonia (UIP). This histopathological pattern is the hallmark of:

• A Nonspecific interstitial pneumonia (NSIP)
• B Cryptogenic organising pneumonia (COP)
• C Respiratory bronchiolitis-ILD
• D Idiopathic pulmonary fibrosis (IPF) ✓

Explanation

Usual interstitial pneumonia (UIP) is the pathological pattern specific to idiopathic pulmonary fibrosis (IPF). The hallmark is the temporal and spatial heterogeneity — dense fibrosis, honeycombing, and fibroblastic foci (young actively proliferating fibroblasts) are seen adjacent to areas of nearly normal lung, all in the same biopsy. This contrasts with NSIP (uniform, temporally homogeneous fibrosis/inflammation without honeycombing), COP (polypoid intraluminal fibrosis in bronchioles/alveoli), and RB-ILD (peribronchiolar macrophage accumulation in smokers).

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

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Written and medically reviewed by the StethoPrep medical team.