Histopathology of human coronary plaque progression, part 1 of 2. (A) Intimal thickening is normal in all age groups and is characterized by smooth muscle cell accumulation within the intima. (B) Intimal xanthoma or so-called fatty streak corresponds to the accumulation of predominantly macrophages within the intima; these lesions have been shown to regress in later adult life. (C) Pathologic intimal thickening marks the first of the progressive lesions and denotes the accumulation of extracellular lipid in the absence of apparent necrosis. (D) Fibrous cap atheroma indicates the presence of an encapsulated necrotic core. (E) The core may eventually become thinned (thin-cap fibroatheroma). (F) This lesion may rupture, allowing contact of the contents of the necrotic core, causing a luminal thrombosis.