Table 1.

Semiquantitative grading scale for the histology score of human endarterectomy specimen.

Grade	0	1	2	3	4
Necrotic Core	No sign of necrotic core	<20% of the arterial area	20–40% of the arterial area	40–70% of the arterial area	>70%
Calcification	No sign of calcification	<10% of the arterial area	10–40% of the arterial area	>40% of the arterial area
Foam Cells	No sign of foam cells	Small * A few small sized clusters (~5) of foam cells	Intermediate * Multiple small (~5) or medium sized (~10) clusters of foam cells	Large * At least 1 large sized cluster (~15) of foam cells or foam cells scattered around ~70% of the arterial area
Cholesterol Crystal	No sign of cholesterol crystal	<10% of the necrotic core	10–40% of the necrotic core	>40% of the necrotic core
Neovasculari-zation	No sign of neovasculari-zation	<25 neovessels in the whole tissue	25–50 neovessels in whole tissue	>50 neovessels in the whole tissue
Inflammatory Cells	No sign of inflammatory cells	Small * A few (1 or 2) small sized (~50 cells) clusters of inflammatory cells or a few cells occasionally spread throughout the arterial area	Intermediate * Multiple (~5) small sized (~50 cells) clusters of inflammatory cells	Large * At least 1 large sized (~100 cells) cluster of inflammatory cells or cells scattered around ~70% of the arterial area
Shoulder	Not detectable *	No sign of shoulder regions	One sided shoulder region	Two-sided shoulder region
Intraplaque hemorrhage (IPH)	No sign of IPH	<10% IPH of the arterial area	10–40% IPH of the arterial area	>40% IPH of the arterial area
SMC-rich ECM area of total ECM area	No SMC visible	<20% of the ECM area	20–40% of the ECM area	>40% of the ECM area
Luminal thrombosis	No	Yes (rupture)

SMC—smooth muscle cell; ECM—extracellular matrix.