to diminish in size. While IHs were previously thought to improve by about 10% each year, newer evidence suggests that maximal improvement and involution is typically reached by 3.5 years of age. Most IHs resolve by age 10, but in some patients, the hemangioma does not completely resolve. Residual redness may be noted and can be improved with laser therapy, most commonly PDL. Ablative fractional resurfacing may be considered for textural skin changes. Hemangiomas, especially those that have gotten very large during the growth phase, may leave behind stretched skin or fibrofatty tissue that may be disfiguring or require future surgical correction. Areas of prior ulceration may leave behind permanent scarring. Additional long-term sequelae stem from the identification of extracutaneous manifestations in association with the IH. For example, a patient with a large facial hemangioma who is found to meet criteria for PHACE syndrome will require potentially ongoing neurologic, cardiac, and/or ophthalmologic monitoring. In cases of IHs that compromise of vital structures, symptoms may improve with involution of the hemangioma. For example, respiratory distress would improve with involution of a space-occupying IH involving the airway and high-output heart failure may lessen with involution of a hepatic hemangioma and ultimately treatment may be tapered or discontinued. In other cases, such as an untreated eyelid hemangioma, resultant amblyopia does not improve with involution of the cutaneous lesion. For these reasons, infants with infantile hemangiomas should be evaluated by an appropriate clinician during the early proliferative phase so that risk monitoring and treatment be individualized and outcomes can be optimized. Terminology The terminology used to define, describe, and categorize vascular tumors and malformations has changed over time. The term hemangioma was originally used to describe any vascular tumor-like structure, whether it was present at or around birth or appeared later in life. In 1982, Mulliken and Glowacki proposed a new classification system for vascular anomalies which has been widely accepted and adopted by the International Society for the Study of Vascular Anomalies. This classification system was recently updated in 2015. The classification of vascular anomalies is now based upon cellular features, natural history, and clinical behavior of the lesion. Vascular anomalies are divided into vascular tumors/neoplasms which include infantile hemangiomas, and vascular malformations that include entities with enlarged or abnormal vessels such as capillary malformations (port wine stains), venous malformations, and lymphatic malformations. In 2000, GLUT-1, a specific immunohistochemical marker, was found to