Mast cells in hemangioma: a double-edged sword.

Hemangioma is a common benign vascular tumor characterized by presentation within the few weeks of life, rapid growth during the first year and spontaneous involution over a period of several years. Mast cells play an important role in immunity and angiogenesis by synthesizing and releasing a group of bioactive mediators, cytokines and chemokines. Previous study confirmed that the number of mast cells is highest during the involuting phase, lower in the involuted phase, and lowest in the proliferating phase. There is evidence that several mast cell mediators are angiogenic by regulating endothelial cell proliferation and degrading the extracellular matrix. Mast cells may also secrete antiangiogenic modulators in the involuting stage of hemangioma. It could be postulated that mast cells may play both angiogenic and antiangiogenic roles in different stage of hemangioma. The mast cell secretion may trigger the "angiogenic switch", while the angiogenic roles may function through the other potential angiogenic factors. Better understanding of the exact role of mast cells in hemangioma will contribute to build new therapeutic interventions targeting mast cells in hemangioma.