At autopsy, a patient who died 5 days after an acute MI shows a soft, yellow-tan infarct with a neutrophilic infiltrate and beginning macrophage infiltration. Which additional finding is expected at this stage?
- A Granulation tissue at the periphery with ingrowth of capillaries and macrophages ✓
- B Dense collagen deposition forming a firm white scar
- C Coagulative necrosis with preserved cellular architecture on low power
- D Contraction bands with eosinophilic wavy fibres visible on H&E
Correct answer: A. Granulation tissue at the periphery with ingrowth of capillaries and macrophages
Explanation
By days 3–7 post-MI, the peak of neutrophilic infiltration begins to wane and macrophage infiltration with phagocytosis of necrotic debris commences. At the periphery of the infarct, granulation tissue with neovascularisation begins to appear. Dense scar formation occurs at 6–8 weeks. Coagulative necrosis with preserved architecture is the earliest finding (first 12–24 hours); contraction bands are an early (first few hours) reperfusion-injury finding.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
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