Hemangioendothelioma of frontal bone.

Radiographic studies disclosed that a 5-year-old girl with proptosis and inferior displacement of her left globe had a lytic lesion in the superior orbital rim. Tissue removed at the time of the initial biopsy was not sufficiently distinctive for a definitive diagnosis, but microscopic examination of residual tumor clearly established the diagnosis of hemangioendothelioma of the frontal bone. Electron microscopic studies demonstrated that the vascular structures, which resembled endothelium, contained many thin microfilaments and mitochondria and scattered dense bodies. Each vessel was surrounded by a prominent mantle of pericytes.