Hemangioma: A birth irregularity where a localized tissue mass grows rich in small blood vessels. Capillary hemangiomas are composed nearly entirely of tiny capillary vessels. Cavernous hemangiomas are composed of blood- filled "lakes" and channels.
An hemangioma may be visible through the skin as a birthmark, known colloquially as a "strawberry mark." Most hemangiomas that occur at birth disappear after a few months or years.