Inflammation of the atherosclerotic cap and shoulder of the plaque is a common and locally observed feature in unruptured plaques of femoral and coronary arteries

Retrospectively, plaque rupture is often colocalized with inflammation of t he cap and shoulder of the atherosclerotic plaque. Local inflammation is th erefore considered a potential marker for plaque vulnerability. However, hi gh specificity of inflammation for plaque rupture is a requisite for applic ation of inflammation markers to detect rupture-prone lesions. The objectiv e of the present study was to investigate the prevalence and distribution ( local versus general) of inflammatory cells in nonruptured atherosclerotic plaques. The cap and shoulder of the plaque were stained for the presence o f macrophages and T lymphocytes in 282 and 262 cross sections obtained from 74 coronary and 50 femoral arteries, respectively. From most cases, 2 athe rosclerotic arteries were studied to gain insight into the local and system ic distribution of the inflammatory process. In 45% and 41% of all cross se ctions, staining for macrophages was observed in the femoral and coronary a rteries, respectively. Rupture of the fibrous cap was observed in 2 femoral and 3 coronary artery segments and was always colocalized with inflammator y cells. At least 1 cross section stained positively for CD68 or acid phosp hatase in 84% and 71% of all femoral and coronary arteries, respectively. O nly 1 femoral and 6 coronary arteries revealed a positive stain for CD68 in all investigated segments. Inflammation of the cap and shoulder of the pla que is a common feature, locally observed, in atherosclerotic femoral and c oronary arteries. The high prevalence of local inflammatory responses shoul d be considered if they are used as a diagnostic target to detect vulnerabl e, rupture-prone lesions.