Melanoma of the Choroid and Ciliary Body
Choroidal and ciliary body melanomas (posterior uveal melanomas) are the most common primary intraocular malignancies in adults. Approximately 6700–7100 new cases of uveal melanomas are reported annually worldwide, of which 65% affect non-Hispanic whites; 87,000–106,000 survivors are under follow-up care. The incidence varies by age, ethnicity, and latitude. The incidence based on ethnicity ranges from 0.4 cases per million people of Asian descent to 1.7 cases per million in Hispanics and 6.0 cases per million in non-Hispanic whites. Among whites, the incidence is higher in those living in regions at higher latitudes. From south to north, the incidence increases from 4.6 to 7.5 cases per million, respectively, in the United States and from 2.6 to 8.4 cases per million, respectively, in Europe.
Fewer than 1% of choroidal and ciliary body melanomas are diagnosed in children younger than 18 years. Approximately 80% of choroidal and ciliary body melanomas are found in adults between 45 and 80 years of age. In the United States and Europe, the mean age at diagnosis is 60–65 years, whereas in Asia it is 45–50 years.
Additional risk factors for posterior uveal melanoma include the following:
light complexion (light skin, blue eyes, blond hair) and an inability to tan
ocular melanocytic abnormalities including nevi (lifetime risk = 1 in 500) and congenital ocular and oculodermal melanocytosis (lifetime risk = 1 in 400)
dysplastic nevus syndrome (three-fold risk)
BAP1 germline mutation or other genetic predisposition
The role of UV radiation as a risk factor for posterior melanoma remains unclear, although most studies conclude that UV light does not play a role. UV light may even be protective because it increases production of vitamin D, which is thought to lower the risk of cancers in tissues not exposed to direct sunlight.
Krantz BA, Dave N, Komatsubara KM, Marr BP, Carvajal RD. Uveal melanoma: epidemiology, etiology, and treatment of primary disease. Clin Ophthalmol. 2017;11:279–289.
The typical choroidal melanoma is a variably pigmented, elevated, dome-shaped mass (see Fig 17-5). Initial symptoms and signs may deceptively resemble those of vitreous detachment, although metamorphopsia, reduced vision, and a visual field defect from direct tumor growth or secondary retinal detachment may eventually develop depending on the location of the tumor. In many patients, however, choroidal melanomas are asymptomatic and are identified incidentally on routine dilated eye examination. Significant growth of a preexisting choroidal nevus or emergence of surface lipofuscin or subretinal fluid should prompt concern for malignant transformation into melanoma (see Fig 17-6).
The degree of pigmentation ranges from amelanotic to dark brown. At the RPE level, clumps of lipofuscin may be present over the surface of smaller tumors (see Figs 17-5A, B and 17-6B, D). Surface lipofuscin appears orange on pigmented tumors but is dark on amelanotic tumors. Localized subretinal fluid is common with melanomas, and larger tumors may be associated with more extensive serous detachment of the neurosensory retina (see Fig 17-5G, H). With time, 50% of tumors erupt through Bruch membrane and assume a mushroom or collar-button shape (see Fig 17-5D, E, G). This process may be associated with subretinal hemorrhage. Some tumors also erode through the retina, causing vitreous hemorrhage or vitreous seeding of a tumor (see Fig 17-5F). If extensive retinal detachment develops, anterior displacement of the lens–iris diaphragm and secondary angle-closure glaucoma occasionally occur. With larger tumors, neovascularization of the iris may occur.
Because they are located posterior to the iris, ciliary body melanomas often remain asymptomatic until they become rather large (Fig 17-7A). Symptoms and signs eventually include a dilated, often tortuous, episcleral vessel(s) (sentinel vessel) in the region of the tumor (Fig 17-7B); reduced vision from induced astigmatism or cataract when the tumor touches the lens; photopsia and visual field alterations from associated retinal detachment in more advanced cases; and, in rare cases, secondary glaucoma.
Ciliary body melanomas are not usually visible unless the pupil is widely dilated. Some erode through the iris root into the anterior chamber and become visible during gonioscopy (Fig 17-7C) or external examination (Fig 17-7D). Eventually, the tumor extends through the sclera along aqueous drainage channels, producing an epibulbar nodule (Fig 17-7E). Some ciliary body melanomas assume a diffuse growth pattern and extend up to 360° around the eye; in this case, they are known as ring melanomas (Fig 17-7F).
Figure 17-7 Ciliary body melanoma, clinical appearance. A, Ciliary tumors are often not evident unless the pupil is widely dilated. They may indent the lens. B, Sentinel episcleral vessels. C, Anterior extension of a ciliary body melanoma may be visible only with gonioscopy (arrows). D, The tumor may invade the anterior chamber. E, The tumor may extend through the sclera (arrow) via emissary channels. F, Ring melanoma grows circumferentially within the ciliary body and may extend into the anterior chamber.
(Courtesy of Tero Kivelä, MD.)
Excerpted from BCSC 2020-2021 series: Section 4 - Ophthalmic Pathology and Intraocular Tumors. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.