Table 1

Modified American Heart Association classification based on morphological description

DescriptionThrombosis
Reproduced from Virmani et al,4 with permission.
Non-atherosclerotic intimal lesions
Intimal thickeningThe normal accumulation of smooth muscle cells (SMCs) in the intima in the absence of lipid or macrophage foam cellsAbsent
Intimal xanthoma, or “fatty streak”Luminal accumulation of foam cells without a necrotic core or fibrous cap. Based on animal and human data, such lesions usually regress.Absent
Progressive atherosclerotic lesions
Pathological intimal thickeningSMCs in a proteoglycan-rich matrix with areas of extracellular lipid accumulation without necrosisAbsent
ErosionLuminal thrombosis; plaque same as aboveThrombus mostly mural and infrequently occlusive
Fibrous cap atheromaWell formed necrotic core with an overlying fibrous capAbsent
ErosionLuminal thrombosis; plaque same as above; no communication of thrombus with necrotic coreThrombus mostly mural and infrequently occlusive
Thin fibrous cap atheromaA thin fibrous cap infiltrated by macrophages and lymphocytes with rare SMCs and an underlying necrotic coreAbsent; may contain intraplaque haemorrhage/fibrin
Plaque ruptureFibroatheroma with cap disruption; luminal thrombus communicates with the underlying necrotic coreThrombus usually occlusive
Calcified noduleEruptive nodular calcification with underlying fibrocalcific plaqueThrombus usually non-occlusive
Fibrocalcific plaqueCollagen-rich plaque with significant stenosis usually contains large areas of calcification with few inflammatory cells; a necrotic core may be presentAbsent