Infantile hemangioma: the common and enigmatic vascular tumor

Infantile hemangioma (IH) is a benign vascular tumor that occurs in 5% of newborns. The tumor follows a life cycle of rapid proliferation in infancy, followed by slow involution in childhood. This unique life cycle has attracted the interest of basic and clinical scientists alike as a paradigm for vasculogenesis, angiogenesis, and vascular regression. Unanswered questions persist about the genetic and molecular drivers of the proliferating and involuting phases. The beta blocker propranolol usually accelerates regression of problematic IHs, yet its mechanism of action on vascular proliferation and differentiation is unclear. Some IHs fail to respond to beta blockers and regrow after discontinuation. Side effects occur and long-term sequelae of propranolol treatment are unknown. This poses clinical challenges and raises novel questions about the mechanisms of vascular overgrowth in IH.