A neoplasm derived from blood vessels, characterized by numerous prominent endothelial cells that occur singly, in aggregates, and as the lining of congeries of vascular tubes or channels. Hemangioendotheliomas are relatively rare and are of intermediate malignancy (between benign hemangiomas and conventional angiosarcomas). They affect men and women about equally and rarely develop in childhood. (From Stedman, 25th ed; Holland et al., Cancer Medicine, 3d ed, p1866)

A vascular proliferation characterized by the presence of prominent endothelial cells and the formation of vascular channels. Hemangioendotheliomas may display borderline or low grade characteristics.

The term hemangioendothelioma describes several types of vascular neosplasms and includes both non-cancerous (benign) and cancerous (malignant) growths. The term has also been applied to those that show "borderline" behavior, intermediate between entirely benign hemangiomas and highly malignant angiosarcomas. Hemangioendotheliomas are...