Orbital arteriovenous malformation with secondary capillary angiomatosis treated by embolization with silastic liquid.

A 19-year-old Caucasian man developed signs of an orbital arteriovenous malformation, which was biopsied and then treated by embolization with a rapidly polymerizing silastic liquid. The biopsy from the initial specimen showed arteries and veins that were malformed with irregular elasticas and muscularis thicknesses, but the most curious feature was a secondary endothelial cell proliferation of such proportions as to simulate in various fields a capillary hemangioma of childhood. Approximately 50% of the bulk of the tumor was the result of the secondary endothelial cell proliferation, which we presume occurred in response to the irritative circumstances of increased intracapillary pressure from the high blood flow between the abnormal arteries and veins. Four years after the tumor was treated with the silastic liquid, it recurred and was again removed surgically. On this occasion, the histopathologic study of the tissues demonstrated a persistent secondary capillary angiomatosis, as well as chronic inflammatory reaction and granulomatous response surrounding the entrapped fragments of the polymerized silastic liquid.