Is a carotid artery plaque a blood clot?

You don’t need to worry excessively about this, as the current issue involves only atherosclerotic plaque—not yet a thrombus—though the two are distinct. Plaque consists of fatty deposits or impurities in the blood that accumulate on the inner walls of blood vessels, forming a localized tissue mass. If such plaques grow large enough—or break loose and travel via the bloodstream to various parts of the body—they may cause thrombosis. For instance, if a dislodged plaque reaches the brain, it can cause a cerebral thrombosis; if it lodges in a coronary artery, it may trigger a myocardial infarction.