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Vascular tumors in children are rare and their classification has been difficult, especially in the pediatric population, because of their unusual morphologic appearance, diverse clinical behavior, and lack of independent stratification for pediatric tumors in the World Health Organization’s (WHO) 2013 classification system. In 2014, the International Society for the Study of Vascular Anomalies (ISSVA) updated their classification system. Although the ISSVA classification of vascular tumors is based on the WHO classification (refer to Tables 458-1 and 458-2), it uses more precise terminology and phenotypes.
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Infantile Hemangiomas
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Infantile hemangiomas are the most common benign vascular tumor of infancy, occurring in 3% to 10% of infants. They are not usually present at birth but are diagnosed most commonly at age 3 to 6 weeks of age. These lesions proliferate for an average of 5 months, then stabilize, and involute over several years. Hemangiomas, which are more common in females, white non-Hispanic patients, premature infants, and multiple gestations, are associated with advanced maternal age and placental complications.
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Hemangiomas are composed of a proliferating, clonal population of endothelial-like cells. During proliferation, provasculogenic factors, such as vascular endothelial growth factor (VEGF), fibroblast growth factor (FGF), CD34, CD31, CD133, LYVE-1, and insulin-like growth factor 2, are expressed. An increase in expression of markers of apoptosis is observed during involution.
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Infantile hemangiomas can be associated with complex syndromes such as PHACE syndrome (Posterior fossa anomalies, Hemangioma, Arterial anomalies, Cardiac Anomalies, and Eye anomalies) or PELVIS syndrome (Perineal hemangioma, External genitalia malformation, Lipomyelomeningocele, Vesicorenal abnormalities, Imperforate anus, and Skin tags). PELVIS syndrome is also described by the acronym LUMBAR syndrome (Lower body hemangioma or other cutaneous findings, Urogential anomalies/ulceration, Myelopathy, Bony deformities, ...