Lymphangioma: Often apparent in the first decade of life, this relatively uncommon tumor consists of large serum filled spaces lined by endothelial cells.  The lesions can be located deep within the orbit or in the eyelids. With valsalva or a upper respiratory tract infection, lymphangiomas may increase in size and be more noticeable.  However, patients may not be aware of the lesion until there is an abrupt onset of proptosis.  This is due to hemorrhage from capillaries into the serum filled spaces, often described as a "chocolate cyst".  In younger children, if the lesion is large, strabismus and ambylopia can be a problem. CT scans can vary in presentation. This patient has a mass in the lateral cone that is compressing the globe. Since the lesion is vascular, not encapsulated and often infiltrates around normal orbital structures, complete resection is usually not successful and debulking is only performed in severe cases. Histopathologically, the endothelial-lined spaces have no pericytes or smooth muscle in the in their wall.  There are scattered follicles of lymphoid tissue with interstitial capillaries throughout. Back to Orbit