Malignant melanoma of the iris can occur as a localized or diffuse pigmented (melanotic) or nonpigmented (amelanotic) lesion.

Critical

Unilateral brown or translucent iris mass lesion exhibiting slow growth. It is more common in the inferior half of the iris and in light-skinned individuals. Rare in Black patients (see Figure 5.14.1).

Figure 5.14.1: Iris melanoma.

Other

A localized melanoma is usually >3 mm in diameter at the base and >1 mm in depth with a variable prominent feeding vessel. Can produce a sector cortical cataract, ectropion iridis, spontaneous hyphema, seeding of tumor cells into the anterior chamber, or direct invasion of tumor into the trabecular meshwork and secondary glaucoma. A diffuse melanoma causes progressive darkening of the involved iris, loss of iris crypts, angle invasion, and increased IOP. Focal iris nodules can be present.

Melanotic Masses

• Nevi: Typically become clinically apparent at puberty, usually flat or minimally elevated (i.e., <1 mm) and uncommonly exceed 3 mm in diameter. Can cause ectropion iridis, sector cortical cataract, or secondary glaucoma. Usually not vascular. More common in the inferior half of the iris. Nevi do not usually grow.

• Tumors of the iris pigment epithelium: Usually black, in contrast to melanomas, which are often brown or amelanotic. Found on the posterior aspect of the iris.

Amelanotic Masses

• Metastasis: Grows rapidly. More likely to be multiple or bilateral than melanoma. Frequently liberates cells and produces a pseudohypopyon. Involves the superior and inferior halves of the iris equally.

• Leiomyoma: Amelanotic and vascular. Difficult to distinguish from an amelanotic melanoma.

• Iris cyst: Unlike melanoma, most transmit light with transillumination. Can arise from the iris pigment epithelium or within the iris stroma. Each has very different clinical features.

• Inflammatory granuloma: Sarcoidosis, tuberculosis, juvenile xanthogranuloma, and others. Often have other signs of inflammation such as keratic precipitates, synechiae, and posterior subcapsular cataract. A history of iritis or a systemic inflammatory disease may be elicited. See Chapter 12, Uveitis.

Diffuse Lesions

• Congenital iris heterochromia: The darker iris is present at birth or in early childhood. It is nonprogressive and usually is not associated with glaucoma. The iris has a smooth appearance. Can be associated with ocular melanocytosis.

• Fuchs heterochromic iridocyclitis: Asymmetry of iris color, mild iritis in the eye with the lighter-colored iris, usually unilateral. Often  associated with a cataract or glaucoma. See 12.1, Anterior Uveitis (Iritis/Iridocyclitis).

• Iris nevus syndrome: Corneal edema, peripheral anterior synechiae, iris atrophy, or an irregular pupil can be present along with multiple iris nodules and glaucoma.

• Pigment dispersion: Usually bilateral. The iris is rarely heavily pigmented (although the trabecular meshwork can be), and iris transillumination defects are often present. See 9.9, Pigment Dispersion Syndrome/Pigmentary Glaucoma.

• Hemosiderosis: A dark iris can result after iron breakdown products from old blood deposits on the iris surface. Patients have a history of a traumatic hyphema or vitreous hemorrhage.

• Siderosis from a retained metallic foreign body.

1. History: Previous cancer, ocular surgery, or trauma? Weight loss? Anorexia?

2. Slit-lamp examination: Carefully evaluate the irides. Check IOP.

3. Gonioscopy.

4. Dilated fundus examination using indirect ophthalmoscopy.

5. Transillumination of iris mass (helps differentiate epithelial cysts that transmit light from pigmented lesions that do not).

6. Photograph the lesion and accurately draw it in the chart, including dimensions. UBM and AS-OCT can be helpful.

Treatment/Follow-Up

1. Observe the patient with periodic examinations and photographs every 3 to 12 months, depending on the suspicion of malignancy.

2. Surgical resection is indicated if growth is documented, the tumor interferes with vision, or it produces intractable glaucoma.

3. Diffuse iris melanoma with secondary glaucoma may require enucleation.

NOTE Avoid filtering surgery for glaucoma associated with possible iris melanoma because of the high risk of tumor dissemination.