A benign tumor, made up of an overgrowth of BLOOD VESSELS. It is extremely common, occurring mostly in infancy and childhood. It can occur anywhere in the body but is most frequently noticed in the SKIN and SUBCUTANEOUS TISSUE. About 75% are present at birth, and about 60% occur in the head and neck area. (from Stedman, 25th ed; DeVita Jr et al., Cancer: Principles & Practice of Oncology, 3d ed, p1355).