Etiology
Any solid tumor in the body that can metastasize via the hematogenous route can metastasize to the orbit.
This definition therefore excludes hematopoietic diseases and systemic lymphoma, as well as direct extension from the skin, eye, intracranial cavity and brain, paranasal sinuses, nasopharynx, and mandible.
Epidemiology
- Adult orbital metastases
- The most common ocular metastases are to the choroid.
- Metastases to the globe are about 8 times more common than to the extraocular orbit (Char, Br J Ophthalmol 1997).
- About 0.7 to 12% systemic cancers metastasize to the orbit (Shields, OPRS 2001; Font, AFIP 2006), of which breast carcinoma accounts for 50% (Shields, OPRS 2001).
- About 47%–91% of orbital metastases are accompanied by metastases in other sites (Ahmad, Curr Opin Ophth 2007).
- By some accounts, orbital metastases might be the second most common form of orbital cancer seen in the adult population after lymphoma (Font, AFIP 2006).
- Orbital metastases constitute 3% of all orbital diseases and 10% of orbital neoplasms in most series.
- Mean interval between diagnosis of primary tumor and the first orbital symptoms has been as long as 60 months.
- About 20% of metastatic tumors to the orbit were the first sign of cancer, and in 10%, the primary site could not be demonstrated (Goldberg, Surv Ophthal 1990).
- More than 90% of orbital metastases are unilateral (Shields, OPRS 2001); in other words, less than 10% have bilateral metastases.
- As cancer patients survive longer, the incidence of orbital metastasis is expected to rise.
- Pediatric orbital metastases
- In children, metastases to the orbit occur more frequently than to the globe (in contrast to adults).
- Neuroblastoma and Ewing's sarcoma are the most common sources of metastatic disease to the orbit (Albert, 2008) in children.
- Medulloblastoma and Wilms' tumor metastasize to the orbit less frequently than neuroblastoma and Ewing's sarcoma (Fratkin, JAMA 1977).
- Orbital metastasis is the initial sign of abdominal neuroblastoma in 3%–4% of patients (Lau, Neuro-ophthal 2004).
- The most common site of primary tumor is the adrenal gland for patients with orbital involvement (Albert, 2008).
- Most cases (90%) occur before 5 years of age, and the prognosis is best in children younger than 1 year of age.
History
- Adults
- A history of enlarging mass, proptosis, diplopia, and pain, usually in a patient with a known history of cancer
- Compared to primary tumors of the orbit, metastatic tumors most commonly present with diplopia (Font, AFIP 2006).
- Gaze-evoked amaurosis has been reported with metastatic breast tumors (Patel, OPRS 2013).
- Rarely, metastatic lesions are found incidentally on imaging—in contrast to benign tumors, where incidental findings are more common.
- Children
- Neuroblastoma commonly presents as rapidly expanding exophthalmos with eyelid ecchymoses (Figure 1).
Figure 1. Bilateral metastatic neuroblastoma.
Clinical features
- Adult orbital metastases
- Rapid onset of symptoms, progressive over weeks or months.
- Diplopia: extraocular muscle infiltration is common due to the high blood flow.
- Blepharoptosis: from levator palpebrae superioris infiltration or compression
- Proptosis: mass effect
- Edema: from compression of venous outflow
- Chemosis: from compression of venous outflow
- Enophthalmos: associated with sclerotic tumors such as scirrhous breast carcinoma and gastric carcinoma (BCSC orbit)
- Imaging
- Lytic bony lesions can be seen on CT scans.
- Breast carcinoma and malignant melanoma have a strong tendency to metastasize to orbital fat and extraocular muscles, while prostate and thyroid carcinomas have a predilection for bone (Figure 2).
- Lateral and superior orbit are the most commonly affected quadrants (Valenzuela, Orbit 2009)
- Metastatic melanoma might have left-sided preponderance, possibly due to direct branching of the left internal carotid from the aortic arch (Figure 3).
- Pediatric orbital metastases
- Metastatic neuroblastoma
- Frequently bilateral, with involvement of the temporal orbit with a lytic bone lesion
- 75% of children with neuroblastoma have proptosis or ecchymoses
- Can rarely cause bilateral blindness from intracranial compression of the optic nerves
- Can also be associated with paraneoplastic signs of opsoclonus and myoclonus
- Metastatic Ewing's sarcoma
- Occurs in the second decade with sudden onset of proptosis due to hemorrhagic metastasis originating from bone
- Most commonly unilateral
Figure 2. T1-weighted MRI of metastatic breast carcinoma infiltrating the right orbital fat (Patel, OPRS 2013).
Figure 3. Metastatic cutaneous melanoma appearing as a discrete left orbital ovoid homogeneous mass with intense rim enhancement (Greene, OPRS 2014).
Testing
General review of systems, including weight loss, fatigue, or other systemic questions, should be elicited with referral to the primary physician or oncologist for further workup, as appropriate.
Initial imaging studies might include CT or MRI of the orbit, which allows for localization of the tumor within the orbit and any bony changes.
MRI has not been found to be superior to CT to establish the diagnosis of metastasis (Char, Br J Ophthalmol 1997), although modern techniques might improve MRI yield.
If there is no previous known history of cancer, a total body positron emission tomography (PET) scan or computed tomography (CT) of chest, abdomen, and pelvis as well as mammography and colonoscopy might also be indicated to look for a primary cancer.
Elevated serum levels of carcinoembryonic antigen (CEA) might suggest a metastatic process.
With carcinoid tumor, functioning metastases can be detected by the presence of elevated urinary 5‑HIAA (Mehta, Ophthalmology 2006).