Gross and light microscopic features of plaque rupture

Gross and light microscopic features of plaque rupture.
(A) Gross photograph of a coronary artery in cross-section showing site of plaque rupture (arrow) with an underlying necrotic core (NC) and luminal thrombus (Th).
(B) Histologic section of the artery in A shows the rupture site (arrows), necrotic core (NC), and luminal thrombus (Th) (Movat pentachrome, x20).
(C) Higher-power view of the fibrous cap shows disruption (arrow), where there is communication of the luminal thrombus (Th) with the underlying necrotic core (NC) (x200).
(D) Higher-power view of the thin fibrous cap shows a paucity of smooth muscle cells (α-actin, brown reaction product, x200).
(E, F) The fibrous cap is heavily infiltrated by macrophages and T-lymphocytes (CD68 and CD45Ro, respectively) (x200).
(G) The strong expression of HLA-DR (an antigen expressed in activated cells), particularly in macrophages and T-cells of the fibrous cap.