Treatment of Iris Melanoma

Melanocytic stromal proliferations and nevi of the iris are the most common tumors of the iris, but melanoma is rare.[1,2] Clinical differentiation between an iris nevus and a melanoma might sometimes be difficult and, at times, impossible. Melanomas of the iris are usually small discrete lesions, although they may occasionally be diffuse, infiltrative, or multiple and may result in heterochromia, chronic uveitis, or spontaneous hemorrhage into the anterior chamber of the eye (hyphema). Iris melanomas that involve more than 66% of the angle circumference are associated with secondary glaucoma.[3]

Routine evaluation of iris melanomas includes gonioscopy, transillumination of the globe, and indirect ophthalmoscopy with 360° of scleral depression. Photographic documentation is essential to verify progression in size or growth of the tumor.[4] Anterior segment fluorescein angiography may be helpful to demonstrate the vascularity of the lesion but is not diagnostic. High-resolution ultrasound biomicroscopy can be used to measure small lesions (basal dimensions and thickness) and to assess tumor involvement of the anterior ciliary body, angle, and overlying sclera.[5] The main disadvantage with this technology is its limited penetration of large lesions. In these cases, conventional ultrasonography is more accurate.

In general, patients with iris melanomas have relatively good outcomes. Only about 3% of these melanomas metastasize within 5 years.[1] Iris melanomas are predominantly of the spindle-cell type and are usually smaller in size than posterior melanomas. Clinical features, including prominent tumor vascularity, rapid growth, and heterogeneous pigmentation, are associated with an epithelioid cell component.[6] Involvement of the iridocorneal angles is frequently associated with ciliary body invasion.[6]

Because iris melanomas are rare and have a good prognosis, clinical trials with sufficient power are impractical. Therefore, treatment experience is based principally on case series and case reports. Conservative management is generally advocated whenever possible, but surgical intervention may be justified with unequivocal tumor growth or extensive disease at initial examination.