Histological examination of a coronary plaque removed at autopsy from a 52-year-old man who died suddenly shows a thin fibrous cap, a large lipid core occupying nearly half the plaque area, and numerous inflammatory cells at the shoulder region. Which feature of this plaque most directly explains its tendency to rupture?

• A Extensive smooth muscle cell proliferation within the intima
• B Dense collagenous cap thicker than 200 micrometers
• C Prominent adventitial fat without luminal narrowing
• D Thin fibrous cap with reduced smooth muscle cells and increased matrix metalloproteinase activity ✓

Explanation

Vulnerable or unstable plaques have a thin fibrous cap (less than about 65 micrometers), a large lipid core exceeding roughly 40 percent of plaque volume, increased inflammatory cells, and reduced smooth muscle cells. Inflammatory cytokines and matrix metalloproteinases degrade collagen, weakening the cap until it ruptures, exposing thrombogenic material and causing occlusive thrombus. Option B describes a stable plaque feature, and extensive smooth muscle proliferation with collagen deposition also indicates stability rather than rupture risk.

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.