Hemangioma, a common tumour of infancy, is a benign vascular neoplasm of unknown aetiology. Most are small lesions, but about 10% can expand rapidly and can be life threatening. The nature of the primary defect responsible for the abnormal endothelial proliferation is unknown. In the 15 March Journal of Clinical Investigation, Eileen Boye and colleagues from Harvard Medical School show that hemangiomas are caused by clonal expansion of vascular endothelial cells.

Boye et al isolated abnormal endothelial cells from proliferating hemangiomas in nine infants and tested the DNA for monoclonality using the X-linked human androgen receptor gene assay. All cells proved to be clonal in origin. They also demonstrated that hemangioma-derived endothelial cells differ from normal endothelial cells in their rate of proliferation and migration in vitro, as well as their response to an angiogenesis inhibitor endostatin (J Clin Invest 2001, 107:745-752).

These results indicate for...