Orbital vascular lesions include a spectrum of disorders that have in common one or more of the cellular components of blood vessels: endothelial cells, pericytes, and smooth muscle cells. Beyond that, there are major differences in their frequency, clinical presentation, morbidity, and management. In addition to the local mass effect and possible systemic implications that characterize any orbital tumor, the hemodynamic relationships of orbital vascular lesions influence their clinical behavior and dictate their appropriate management. Whereas every lesion has an intrinsic blood supply to meet its own metabolic needs, some are more closely integrated into the systemic vasculature and convey considerably more blood than needed for their own sustenance.

We prefer to divide vascular lesions between two major categories: developmental malformations and neoplastic proliferations (Table 1). The cellular complement and basic structure of developmental malformations are present at birth, and growth occurs by expansion. The neoplasms, on the other hand, enlarge by proliferation of their component vascular units or predominant cell of origin.