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 may be impossible. Melanomas of the iris are usually small discrete lesions, though they may occasionally be diffuse, infiltrative, or multiple, and they 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.
Routine evaluation of iris melanomas includes gonioscopy, transillumination of the globe, and indirect ophthalmoscopy with 360° of scleral depression. Photographic documentation is essential to document progression in size or growth of the tumor. 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. The main disadvantage with this technology is its limited penetration of large lesions. In these cases, conventional ultrasonography is more accurate.
There is a wide range of treatment approaches, including excision, radiation therapy, cryosurgery, electrodesiccation and curettage, photodynamic or laser-beam light exposure, and topical therapies. Mohs micrographic surgery is a form of tumor excision that involves progressive radial sectioning and real-time examination of the resection margins until adequate uninvolved margins have been achieved, avoiding wider margins than needed. Each of these methods is useful in specific clinical situations...
In general, iris melanomas have relatively good outcomes. Only about 3% of these melanomas develop metastases within 5 years. 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. Involvement of the iridocorneal angles is frequently associated with ciliary body invasion.
Given their rarity and good prognosis, trials with sufficient power are practical. 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 and with extensive disease at initial examination.
Standard treatment options:
Observation with careful follow-up: In asymptomatic patients with stable lesions; follow-up includes serial photography.
Local resection: When progressive and pronounced growth is documented.
Enucleation: If the tumor is not amenable to local resection (diffuse involvement of the iris, involvement of more than 50% of the iris and anterior chamber angle, intractable glaucoma, and extraocular extension).
Plaque radiation therapy: Offered as an alternative for large, diffuse, surgically nonresectable lesions of the iris.