Hemangiopericytoma: (1, 2)This uncommon lesion of the orbit or eyelid usually appears in the fourth or fifth decade and presents as a mass that can cause restriction of motility, displacement of the globe, prolapse of the conjunctiva and engorgement of vessels. The lesion is usually well defined on CT scan and appears bluish at the time of surgery. Since hemangiopericytomas can undergo malignant degeneration, the tumors are usually excised. Microscopically they are encapsulated, hypervascular, hypercellular, plump pericytes with stag horn configurations of vessels. Back to Orbit