The orbit is defined by all the structures that are contained within the bones of the eye socket. This includes the eyeball, extraocular muscles, optic nerve and the fat that fills the spaces in between. Any of these structures can be affected by a tumor. In addition, cancer of the surrounding sinuses, brain, and nasal cavity may grow through the bones and invade the orbit. Metastatic tumors may also travel to the orbit. Orbital tumors can affect both adults and children. Fortunately, in both age groups most orbital tumors are benign.
In children most tumors are the result of developmental abnormalities. The most common benign tumors in children are dermoids (cysts of the lining of bone) and hemangiomas (a blood vessel tumor). Children also commonly suffer from orbital cellulitis, an infection that usually starts as a severe sinusitis and secondarily invades the orbit, resulting in prominence of the eyeball. Malignancies in childhood are unusual (most common is rhabdomyosarcoma), but any rapidly growing mass is cause for concern.
In the adult population the most common benign tumors are also blood vessel tumors (hemangioma, lymphangioma and arteriovenous malformation). Tumors of the nerves (schwannoma), fat (lipoma), as well as those that evolve from the surrounding sinuses (mucocele) occur less commonly. Frequently, pain and prominence of the eyes can be mistakenly attributed to the growth of a tumor. Further evaluation often reveals a benign non-infectious inflammatory process termed pseudotumor (as an indication of the diagnostic confusion associated with this entity). Alternatively the inflammation may result from a systemic process such as Graves' thyroid disease. The most common malignant orbital tumors in adults are lymphomas. Often they are initially confined to the orbit without any systemic manifestations. Metastatic tumors most frequently arise from the breast and prostate. Direct invasion of the orbit from the surrounding skin and sinus cavities can occur from squamous and basal cell cancers. Other malignancies that arise from tissues within the orbit are less common (hemangiopericytoma, chondrosarcoma, malignant neurofibroma).
The evaluation of a patient with a prominent eye begins with a careful history and examination by a specialist trained in the field of orbital diseases. In addition to progressive prominence of one or both eyes, troubling symptoms include pain, loss of vision or double vision, redness and swelling of the eyelids and the presence of a palpable mass. Most often either a CAT scan or MRI will be ordered to more carefully define the condition. If suspicious, a diagnostic biopsy may be required. Some conditions require no treatment, whereas others are best treated medically or with the use of radiation therapy. The remainder require surgical excision. Fortunately, surgery has become safer with the use of CAT scans and MRI for preoperative planning, along with the intraoperative use of operating microscopes and surgical lasers.