Mast cells in hemangiomas and vascular malformations.

Common pediatric vascular birthmarks, classified as hemangiomas or malformations, were analyzed for the presence of mast cells. Hemangiomas in the proliferative phase contained large numbers of mast cells (27 +/- 15 cells/high-power field [HPF]) in comparison with hemangiomas in the involuting phase (2.6 +/- 2.9), vascular malformations (1.7 +/- 3.2), and normal skin (5.0 +/- 1.0). Inasmuch as hemangiomas are characterized by endothelial proliferation and increased numbers of mast cells, these data raise the possibility that mast cells may have an important role in the formation and/or maintenance of these lesions.