The Pathogenesis of Hemangiomas: A Review

Learning Objectives: After reading this article, the participant should be able to: 1. Differentiate between hemangiomas and vascular malformations. 2. Describe arguments for the trophoblast origin of hemangiomas. 3. Give arguments for the angioblast theory for the origin of hemangiomas. 4. Identify key genes involved in the origin of hemangiomas. Background: Hemangiomas of infancy are common endothelial tumors. They differ from vascular malformations in their tissue architecture and biological properties. To date, there is no universally accepted theory that explains the pathogenesis and pathophysiology of hemangiomas. Methods: Theories from the medical literature from 1981 to 2004 were gathered, categorized, and reviewed. Results: Current research is mostly on the cellular and genetic levels. The most authoritative theories focus on angioblast origins, trophoblast origins, mutations in cytokine regulatory pathways, and field defects as the cause of the deranged angiogenesis of hemangiomas. Conclusions: To date, no single theory can easily explain all the characteristics of hemangiomas, such as predilection for the female sex, usual occurrence after birth, spontaneous involution, abnormal tissue architecture, and distribution within a developmental field. Hemangiomas are probably the final common expression of several pathophysiological mechanisms taking effect alone or in combination. (Plast. Reconstr. Surg. 117: 29e, 2006.)