An orbital tumor has the following characteristics: Retrobulbar location within the muscle cone, well defined capsule, presents with slowly progressive proptosis, easily resectable, occurs most commonly in the 2" to 4th decade. The diagnosis is:

Cavernous hemangioma Cavernous hemangioma is the most common benign, intraconal tumor in adults. Hemangiopericytoma is also retro bulbar intraconal lesion. found in adults but is a rare tumor. Moreover owing to its tendency to invade the adjacent tissues, its margins are less distinct than cavernous hemangioma. Rest 2 options i.e. Dermoid and Capillary hemangiomas are primarily extraconal lesions. Cavernous hemangioma Cavernous hemangioma is the most common orbital vascular tumor in adults. Patients are typically middle aged (2nd to 4th decade) Present with slowly progressive painless proptosis Mostly its intraconal (>80%) but may also be extraconal. Cavernous hetnangiomas possess a distinct fibrous pseudo capsule and therefore on CT and MR appear well defined masses. Cavernous hemangioma is easily resectable as it is: - well encapsulated - does not have a prominent aerial supply (in contrast to capillary hemangioma) Capillary hemangioma Capillary hemangiomas occur primarily in infants. The tumor often increases in size for 6 to 10 months and then gradually involutes. Mostly extraconal, commonly occur in superior nasal quadrant. Capillary hemangiomas in and around the orbit may have an aerial supply from either the external carotid or internal carotid aeries. These tumors are capable of profuse bleeding. On CT and MR these lesions appear fairly well marginated to poorly marginated. Hemangiopericytomas Hemangiopericytomas are rare, slow growing vascular neoplasms that arise from the pericytes of Zimmermann, which normally envelop capillaries. About 50% cases are malignant. On CT and MR the orbital hemangiopericytoma, in contrast to cavernous hemangioma, appear less distint owing to its tendency to invade the surrounding tissues. Angiography may differentiate the tumors from cavernous hemangioma, meningioma, and schwannoma. - Hemangiopericytomas usually have an early florid blush - Cavernous hemangiomas show late minor pooling of contrast, or often appear as avascular masses - Meningiomas may show multiple tumor vessels and a late blush - Schwannomas may show no tumor blush. Dermoid Dermoid and epidermoids are the most frequent development cysts of the orbit. They result from the inclusion of ectodermal elements during closure of the neural tube. The dermoid contains one or more dermal adnexal structures such as sebaceous glands and hair folliclels. Dermoids are extraconal lesions. mostly located at the superior temporal quadrant of the orbit. On CT or MR demonstration offat within the lesion is almost diagnostic of dermoid.