Aneurysmal bone cyst of the orbit with unusual angiographic features.

A 14 month old boy with sudden onset of proptosis of the left eye due to an aneurysmal bone cyst of the orbit is reported. Sequential plain films of the orbital region demonstrated changes ranging from subtle loss of bone definition of the orbital margin to the characteristic appearance of an aneurysmal bone cyst twelve months later. Arteriography at the time of the initial evaluation demonstrated prolonged retention of the contrast medium which we believe represents changes secondary to the number of giant cells present in the tumor rather than the relative vascularity of the lesion. While aneurysmal bone cyst of the orbit is extremely rare, it should be included in the differential diagnosis of proptosis in the pediatric age group.