Carotid rupture and intraplaque hemorrhage: Immunophenotype and role of cells involved

Background A complete immunohistochemical characterization in complicated c arotid plaques is still lacking. The cellular components of 165 carotid end arterectomy specimens were analyzed to assess their role in the pathogenesi s of plaque rupture and intraplaque hemorrhage without rupture. Methods and Results The fibrous caps at the sites of plaque rupture showed CD68+ macrophages, T-lymphocytes, and scarce B-lymphocytes. Ruptured plaque s showed mononuclear infiltrates in the caps, shoulders, and bases of the p laques in 85% of the cases. Only 46% of nonruptured plaques showed such inf iltrates (P < .0001). Two types of lipid cores were recognized: avascular o r mildly vascularized and highly vascularized. The vessels of the latter ty pe reacted with CD31 and CD34. In 57.5% of the cases, the base and the shou lders of the plaques showed neoformed, CD34+ vessels, often surrounded by m ononuclear infiltrates. Intraplaque hemorrhage without rupture had highly v ascularized lipid cores in all cases. T-lymphocytes and macrophages were in close contact with neoformed vessels. Conclusions Plaque rupture is characterized by mononuclear cell infiltratio n of the caps, whereas intraplaque hemorrhage without rupture is characteri zed by extensive vascularization of the plaque.