High Quality Content by WIKIPEDIA articles! In pathology, an atheroma is an accumulation and swelling in artery walls made up of (mostly) macrophage cells, or debris, and containing lipids (cholesterol and fatty acids), calcium and a variable amount of fibrous connective tissue. Atheroma occurs in atherosclerosis, which is one of the three subtypes of arteriosclerosis (which are atherosclerosis, Monckeberg`s arteriosclerosis and arteriolosclerosis).