The most common birthmark of infancy, the hemangioma is composed of stem cells (embryonic cells that may become many different types of tissue). The hemangioma is considered a benign (non-cancerous) tumor that is congenital but not genetically inherited. The cause of these tumors is unknown but the risk of having one goes up with prematurity, low birth weight, and being an identical or fraternal twin. Hemangiomas occur 80 percent of the time in the head and neck.
Learn more at the New York Head and Neck Institute.