Metastatic cancer probably represents the most common form of intraocular malignancy. There are many large series, reviews, and case reports on metastatic neoplasms to the intraocular structures, and only selected reports are cited here (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56). Even though uveal metastasis is the most common intraocular malignancy, in a practice of ocular oncology it is not encountered so frequently as uveal melanoma, possibly because many affected patients have advanced systemic cancer and do not come to the attention of an ophthalmologist. Metastatic cancer reaches the intraocular structures through hematogenous routes and most commonly develops in the uveal tract, with >90% involving the posterior aspect of the choroid and <10% arising in the iris and/or ciliary body. Metastasis to the retina, optic disc, and vitreous are relatively uncommon.

Most intraocular metastases are carcinomas, with sarcomas and melanomas being less common. The majority of uveal metastases originate from breast cancer in women and lung cancer in men. Less often, the primary malignancy arises from carcinoma of the alimentary tract, kidney, thyroid gland, pancreas, prostate, and other organs. Cutaneous melanoma and bronchial carcinoid tumors occasionally metastasize to the uveal tract and have distinctive features. Of patients who present to the ophthalmologist with uveal metastasis, about 25% have no known history of systemic cancer. After subsequent systemic evaluation, about 10% have no detectable primary cancer, the primary being occult (3). Hence, the clinician should be familiar with the clinical manifestations of intraocular metastatic disease.

The clinical features of an intraocular metastasis vary with the location of the tumor (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56). Iris metastasis appears as single or multiple yellow, white, or pink nodules in the iris stroma. It can appear as one or more circumscribed tumors, or it can be friable and seed cells into the aqueous, producing a clinical picture of intraocular inflammation. A ciliary body metastasis is often more difficult to detect clinically. It can appear as a solitary mass, or it can produce inflammatory signs, simulating iridocyclitis. Choroidal metastasis usually appears as one or more yellow lesions. It has a tendency to affect the posterior choroid, frequently in the macular area. In contrast to iris and ciliary body metastasis, choroidal metastasis tends not to produce inflammatory signs, but it usually causes a quiet secondary serous retinal detachment. Although choroidal metastasis usually has a yellow color, metastasis from melanoma often has a gray or brown color and metastasis from carcinoid tumor, thyroid cancer, and renal cell carcinoma often has an orange color. Retinal metastasis, which is extremely rare, can simulate an occlusive vasculitis and can seed into the vitreous. Vitreous metastasis is also rare and probable derives from the retina. It generally presents with tumor cells in the vitreous, resembling a primary inflammatory process of primary lymphoma. Optic disc metastasis can develop by contiguous spread from juxtapapillary choroidal metastasis, or it can involve only the optic nerve, where it produces a unilateral elevation of the optic disc (9). Secondary glaucoma frequently occurs, particularly with iris and ciliary body tumors.

The diagnosis of intraocular metastasis is generally made by taking a history for prior cancers and by careful slit lamp biomicroscopy and ophthalmoscopy. Ancillary studies such as fluorescein angiography and ultrasonography can be of assistance in diagnosis. Fluorescein angiography of a choroidal metastasis generally shows beginning hyperfluorescence of the mass in the late venous phase, usually later than with choroidal hemangioma or melanoma. With ultrasonography it usually shows high internal reflectivity with A-scan and acoustic solidity with B-scan, a pattern similar to that seen with choroidal hemangioma. In rare instances, a choroidal metastasis can assume a mushroom configuration similar to that of a choroidal melanoma (26). In difficult cases that cannot be diagnosed with the aforementioned methods, fine needle aspiration with cytologic evaluation of aspirate can be used to establish the diagnosis (6).

Most intraocular metastases are diagnosed clinically and no histopathologic material is available. However, uveal metastasis can assume many gross and microscopic patterns (26). Grossly, it is usually white or yellow and sessile, nodular, or diffuse. Histopathology of uveal metastasis varies considerably, depending on the type, primary site, and degree of differentiation (1,2). Some tumors are so poorly differentiated that the primary site is difficult to determine based on examination of the ocular tissue. In such instances, immunohistochemistry may be of some value in classifying the neoplasm and in determining the primary site.

Management options for uveal metastasis vary with the clinical situation (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11,54, 55, 56). Small, asymptomatic tumors or those that have responded to prior or present chemotherapy may require no immediate treatment and can be followed periodically. Larger, symptomatic tumors may require external beam irradiation or plaque radiotherapy.

The systemic prognosis varies with the type of tumor. Patients with choroidal metastasis from breast cancer often have a more favorable prognosis, whereas patients with metastasis from lung cancer or melanoma have a worse prognosis. Patients with metastasis from carcinoid tumor often have a much better prognosis, and metastatic foci from this tumor can remain relatively dormant for months or years (10,23).