Background
Hemangiomas are abnormally dense collections of dilated small blood vessels (capillaries) that may occur in the skin or internal organs. They may be present anywhere on the body. The classically recognized hemangioma is a visible red skin lesion that may be superficial in the skin (in the top layers, called a capillary hemangioma), deeper in the skin (cavernous hemangioma), or a mixture of both. Hemangiomas are usually present at birth although they may appear within a few months of birth often beginning at a site that has appeared slightly dusky or colored differently than the surrounding tissue. Hemangiomas, both deep and superficial, undergo a rapid growth phase in which their volume and size increase rapidly. This phase is followed by a rest phase, in which the hemangioma changes very little, and an involutional phase where the hemangioma undergoes spontaneous regression. During the involutional phase, hemangiomas may disappear completely. Large cavernous hemangiomas distort the skin around them and despite full involution, will ultimately leave visible changes in the skin. The more superficial capillary hemangioma may involute completely, leaving no evidence of its past presence.