Benign tumors of the vascular endothelium. Hemangiomas of infancy are the most common type of hemangiomas, characterized by a unique natural history of growth in early infancy, followed by slow involution over the next several years. Hemangiomas may be present at the time of birth as so-called precursor lesions in approximately half of the cases. Rarely are they fully-formed tumors at birth. In the remainder of cases, lesions become evident after birth, usually within the second and fourth weeks of life.
