Grossly begin as multiple minute flat yellow spots which eventually coalesce into elongated streaks of 1cm long
Microscopically fatty streaks are composed of lipid filled foamy macrophages
Fatty streaks are not much raised to cause significant flow disturbances
All the fatty streaks may not progress to advanced lesions
Atherosclerotic plaque
Intimal thickening and lipid accumulation together form plaques
Grossly atherosclerotic plaques are white yellow and encroach on the lumen of the artery. Later ulcerated plaques are superimposed by thrombus
Atherosclerotic plaques are patchy involving only portion of the arterial wall and rarely circumferential on cross section
Common sites of formation of atherosclerotic plaques in descending order are
Lower abdominal aorta
Coronary arteries
Popliteal arteries
Internal carotid arteries
Vessels of circle of Willis
Atherosclerotic plaques have 3 principle components
Smooth muscle cells, macrophages and T cells
Extracellular matrix including collagen elastic fibres and proteoglycans
Intracellular and extracellular lipids
Typically atherosclerotic plaque have superficial fibrous cap composed of smooth muscle cells and relatively dense collagen
Beneath and side of cap shows more cellular area containing macrophages, T cells and smooth muscle cells
Deep to the fibrous cap is a necrotic core containing lipid (primarily cholesterol and cholesterol esters) debris from dead cells, foam cells (lipid laden macrophages and smooth muscle cells) fibrin, variably organized thrombus and other plasma proteins
Cholesterol presents as crystalline aggregates and are washed out during routine processing and leave behind empty “clefts”
Periphery of the lesion shows neovascularization
References
Vinay kumar, Abul K.Abbas, Nelson Fausto, Jon C. Aster. Robbins and Cotran Pathologic basis of disease. 8th edition.
