The presence of which of the following features in an atherosclerotic plaque indicates that it has become a complicated lesion?

Complicated lesions indicate advanced atherosclerotic disease. They arise in atherosclerotic plaques, and render them more susceptible to sudden occlusion and acute infarction of the supplied tissues. Commonly, the plaque ulcerates or ruptures, and the exposed surfaces, being highly thrombogenic, precipitate thrombus formation. Thrombi are typified by the lines of Zahn, alternating layers of platelets and fibrin (the pale lines) and layers of blood (the dark lines). Beyond thrombus formation, other features of a complicated plaque include hemorrhage into the lesion itself, and microembolism by cholesterol crystals or calcified debris. Fuhermore, the weakened media underlying the plaque may develop an aneurysmal dilatation. In general, the clinical significance of atherosclerosis is related to the consequences of complicated lesions. The incorrect options all include features of atheromatous plaques, but do not indicate complicated lesions:Beneath the endothelium of a plaque there is a fibrous cap composed of smooth muscle, chronic inflammatory cells and lipid laden macrophages (foam cells), as well as extracellular material. The core of the lesion, which lies between the intima and the media, is composed of necrotic cellular debris, with cholesterol crystals, calcium, and more foam cells. Ref: Fuster V., Falk E. (2011). Chapter 52. Atherothrombosis: Disease Burden, Activity, and Vulnerability. In V. Fuster, R.A. Walsh, R.A. Harrington (Eds),Hurst's The Hea, 13e.