Melanocytoma of the Iris, Ciliary Body, and Choroid
Melanocytomas (magnocellular nevi) are rare tumors composed of characteristically large, polyhedral melanocytic cells that have small, bland nuclei and abundant cytoplasm filled with large melanin granules (see Chapter 15, Fig 15-12). Iris melanocytoma cells may seed to the anterior chamber angle, causing glaucoma. Melanocytomas of the ciliary body are usually not seen clinically because of their peripheral location. In some cases, extrascleral extension of a melanocytoma along an emissary canal appears as a darkly pigmented, fixed subconjunctival mass. Melanocytomas of the choroid appear as elevated, pigmented tumors, similar to a nevus or a melanoma. Malignant changes have been reported in some melanocytomas.
When a melanocytoma is suspected, photographic and ultrasonographic studies are appropriate. If growth is documented, biopsy should be considered to exclude melanoma.
Shields CL, Kaliki S, Hutchinson A, et al. Iris nevus growth into melanoma: analysis of 1611 consecutive eyes: the ABCDEF guide. Ophthalmology. 2013;120(4):766–772.
Shields JA, Shields CL, Eagle RC Jr. Melanocytoma (hyperpigmented magnocellular nevus) of the uveal tract: the 34th G. Victor Simpson lecture. Retina. 2007;27(6):730–739.
Figure 17-4 Choroidal nevi, clinical appearance. Choroidal nevi are generally thinner than 2 mm and variably brown. They may be solitary (A) or multiple (B). Nevi may demonstrate drusen on their surface (A,arrow). C, Small nevi lack retinal pigment epithelial (RPE) changes. D, Large nevi usually exhibit RPE changes (note the drusen [arrow] and focal RPE hyperplasia [arrowhead]). E–F, Some nevi display surface lipofuscin, which appears as orange pigment on dark tumors (E,arrows), and pigmented melanolipofuscin on amelanotic tumors (F,arrows) and can be associated with subretinal fluid (E,asterisk). G, Congenital ocular melanocytosis has a diffuse nevus-like dark choroidal appearance. H, Appearance of patchy gray sclera (asterisks) and diffuse iris pigmentation associated with ocular melanocytosis. All of the lesions illustrated in this figure were followed for several years without evidence of growth.
(Parts A, B, F, and H courtesy of Alison Skalet, MD, PhD; parts C–E and G courtesy of Tero Kivelä, MD.)
Figure 17-5 Choroidal melanoma, clinical appearance. A, B, Choroidal melanomas may be quite thin. Note the prominent surface lipofuscin in each case and the large area of flat involvement surrounding the elevated portion centrally in part B(arrowheads); however, they are more commonly elevated (>2 mm in height). Melanomas are usually pigmented (A, B, E, F) or, less commonly, amelanotic (C, D). Smaller melanomas typically have a dome shape, whereas larger tumors that have broken through Bruch membrane have a collar-button configuration (D, E). This is often accompanied by subretinal hemorrhage (D,arrowheads). F, Retinal invasion and vitreous seeding of a tumor may occur, with seeding seen as a dark streak (arrowheads).G, H, Very large tumors may be associated with large serous retinal detachments. In part G, the tumor apex is darkly pigmented (asterisk), and the retinal detachment is seen at the lower left (arrowheads).
(Parts A and H courtesy of Tero Kivelä, MD; parts B–G courtesy of Alison Skalet, MD, PhD.)
Figure 17-6 Malignant transformation of choroidal nevus to melanoma. A, Small choroidal nevus. B, After an observation period of 13 months, the nevus has expanded its borders and acquired surface lipofuscin. C, A different patient with a small peripapillary choroidal nevus. D, The nevus shown in part C demonstrated substantial growth and emergence of surface lipofuscin after an observation period of 6.5 years.
(Courtesy of Alison Skalet, MD, PhD.)
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.