Which combination of morphological features best defines a 'vulnerable' or unstable atherosclerotic plaque that is prone to rupture?
- A Thin fibrous cap less than 65 micrometers, large lipid core exceeding 40 percent of plaque volume, abundant macrophages ✓
- B Thick fibrous cap, small lipid core, dense collagen, few inflammatory cells
- C Extensive calcification, neovascularization limited to the adventitia, eccentric luminal narrowing under 50 percent
- D Concentric smooth muscle proliferation, proteoglycan-rich matrix, minimal necrotic core
Correct answer: A. Thin fibrous cap less than 65 micrometers, large lipid core exceeding 40 percent of plaque volume, abundant macrophages
Explanation
Vulnerable plaques have a thin fibrous cap (less than about 65 micrometers), a large necrolipid core occupying more than 40 percent of plaque area, increased macrophage infiltration releasing matrix metalloproteinases, and reduced smooth muscle content. These features predispose to cap rupture and overlying thrombosis causing acute coronary syndromes. Option B describes a stable plaque, which is more likely to cause chronic exertional angina than sudden occlusion. Extensive calcification alone does not predict instability.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.