Thefibrous cap is a layer offibrous connective tissue, which is thicker and less cellular than the normalintima, found inatheromatous plaques. The fibrous cap containsmacrophages andsmooth muscle cells.^[1] The fibrous cap of anatheroma is composed of bundles of muscle cells, macrophages,foam cells, lymphocytes,collagen and elastin.^[1] An atheroma with a cap is termed afibrous cap atheroma.

The rupture of a fibrous cap can lead to astroke, or aheart attack either of which has the potential to be fatal.^[2]The fibrous cap is prone to rupture and ulceration which can lead to thrombosis. In advanced lesions, further complications may arise including calcification of the fibrous cap.^[3]