Figure 17-2 Choroidal nevi, clinical appearance. A, Choroidal nevus with overlying drusen, under the lower temporal retinovascular arcade. B, Medium-sized choroidal nevus with overlying drusen, superior to the optic nerve head.

(Courtesy of Jacob Pe’er, MD.)

Virtually all choroidal melanocytic tumors thicker than 3 mm are melanomas, and virtually all choroidal melanocytic lesions thinner than 1 mm are nevi. Many lesions 1–2 mm in thickness (apical height) may be benign, although the risk of malignancy increases with height. It is difficult to classify with certainty tumors that are 1–2 mm in thickness. Flat lesions with a basal diameter of 10 mm or less are almost always benign. The risk of malignancy increases for lesions that are larger than 6 mm in basal diameter.

Clinical risk factors for enlargement of choroidal melanocytic lesions have been well characterized and include

subjective clinical symptoms such as metamorphopsia, photopsia, visual field loss presence of orange pigmentation

associated subretinal fluid larger size at presentation juxtapapillary location

absence of drusen or RPE changes hot spots on fluorescein photography

homogeneous, low internal reflectivity on ultrasonography

If definite enlargement is documented, malignant change should be suspected.

The recommended management of choroidal nevi is photographic documentation for lesions less than 1 mm in thickness and photographic and ultrasonographic documentation for lesions greater than 1 mm in thickness, coupled with regular, periodic reassessment for signs of growth.

Melanocytoma of the Iris, Ciliary Body, or Choroid

Melanocytomas are rare tumors composed of characteristic large, polyhedral-shaped cells with small nuclei and cytoplasm filled with melanin granules (see Chapter 15, Fig 15-12). Cells from iris melanocytomas 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 the tumor along an emissary canal appears as a darkly pigmented, fixed subconjunctival mass. Melanocytomas of the choroid appear as elevated, pigmented tumors, simulating a nevus or melanoma. Melanocytomas have been reported to undergo malignant change in some instances. When a melanocytoma is suspected, photographic and echographic studies are appropriate. If growth is documented, the lesion should be treated as a malignancy.

Shields CL, Furuta M, Berman EL, et al. Choroidal nevus transformation into melanoma: analysis of 2514 consecutive cases. Arch Ophthalmol. 2009;127(8):981–987.

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.

Iris Melanoma

Iris melanomas account for 3%–10% of all uveal melanomas. Small melanomas of the iris may be impossible to differentiate clinically from benign iris nevi and other simulating lesions. The following conditions may be included in a differential diagnosis of iris melanoma:

iris nevus

primary iris cyst (pigment epithelial and stromal) iridocorneal endothelial syndrome

iris foreign body

peripheral anterior synechiae metastatic carcinoma to the iris aphakic iris cyst

iris atrophy, miscellaneous

pigment epithelial hyperplasia or migration juvenile xanthogranuloma

retained lens material simulating iris nodule

Signs suggesting malignancy include extensive ectropion iridis, prominent vascularity, sectoral cataract, secondary glaucoma, seeding of the peripheral angle structures, extrascleral extension, lesion size, and documented progressive growth. Iris melanomas range in appearance from amelanotic to dark brown lesions, and three-quarters of them involve the inferior iris (Fig 17-3). In rare instances, they assume a diffuse growth pattern, producing a syndrome of unilateral acquired hyperchromic heterochromia and secondary glaucoma. Clinical evaluation is identical to that for iris nevi. The differential diagnosis of iris nodules is listed in Table 17-1; Figure 17-4 illustrates the various iris nodules. See also Figure 12-11 in Chapter 12.

Advances in high-frequency ultrasonography allow for excellent characterization of tumor size and anatomical relationship to normal ocular structures (Fig 17-5). Fluorescein angiography may document intrinsic vascularity, although this finding is of limited value in establishing a differential diagnosis. In rare instances, biopsy may be considered when the management of the lesion is in question. In most cases, when growth or severe glaucoma occurs, diagnostic and therapeutic excisional treatment is indicated. Brachytherapy using custom-designed plaques may be used in selected cases. Specifically designed proton-beam radiotherapy has also been reported for iris melanoma. The prognosis for most patients with iris melanoma is excellent, with a lower mortality rate (1%–4%) than that for ciliary body and choroidal melanomas, possibly because the biological behavior of most of these iris tumors appears distinctly different from that of ciliary body or choroidal melanoma. Anterior chamber angle invasion increases the risk of metastasis.

Henderson E, Margo CE. Iris melanoma. Arch Pathol Lab Med. 2008;132(2):268–272.

Jakobiec FA, Silbert G. Are most iris “melanomas” really nevi? A clinicopathologic study of 189 lesions. Arch Ophthalmol. 1981;99(12):2117–2132.