Vascular lesions of the orbit: more than meets the eye.

Vascular lesions of the orbit may be classified on the basis of their natural history, growth pattern, and histologic composition as capillary hemangiomas, venous vascular malformations, venous lymphatic malformations, arterial and arteriovenous lesions, or neoplasms. Most follow a characteristic pattern of clinical development and have one or more specific imaging features that allow diagnosis. Hemangiomas typically manifest at or soon after birth and subsequently involute. They are nonencapsulated, poorly circumscribed, often lobulated, and largely extraconal in location. Cavernous malformations are septate and well circumscribed, may exhibit progressive enhancement on delayed images, and do not involute. Orbital varices appear distended on images obtained with the patient prone or during the Valsalva maneuver. Venous lymphatic malformations show multiple fluid-fluid levels, enlarge during viral infections, and may manifest as chocolate-colored cysts after an acute hemorrhage. Arteriovenous malformations, fistulas, and aneurysms have typical angiographic features. Hemangiopericytomas arise from the paranasal sinuses and show early tumor blush and persistent staining on angiographic images. Hemangioblastomas appear as enhancing mural nodules with associated cysts and serpentine flow voids on magnetic resonance (MR) images. Choroidal hemangiomas and melanomas can be differentiated on the basis of their appearances on T2-weighted MR images. Patients with vascular orbital and ocular metastases commonly have a history of breast or lung primary tumors.