Carol L. Shields

Pediatric Considerations

A study of 40 young patients with uveal melanoma (age <20 years) by Shields and associates indicated that iris melanoma in this patient age group is more common (12%) than in adults (4%; ref. 1)[A].

BASICS

DESCRIPTION

• Iris melanoma represents a malignant melanocytic neoplasm arising from the iris stroma. Iris melanoma is uncommon, representing only 4% of all uveal melanomas. In a series of 169 consecutive patients with iris melanoma, elevated intraocular pressure (IOP) was found in 30% of cases. The main mechanism for the elevated pressure was mechanical obstruction of aqueous outflow from solid tumor or seeding (2)[A].

• Iris melanoma has potential to metastasize to liver, lungs, or skin.

• Iris melanoma can assume different clinical presentations such as circumscribed, diffuse, tapioca, or trabecular meshwork configuration. Size, shape, and degree of pigmentation can vary from case to case. Similar to iris nevus, iris melanoma can cause corectopia and ectropion of the pupillary margin. More than 80% of iris melanomas are located in the inferior half of the iris.

– Circumscribed iris melanoma is the most common type and presents as a well-defined mass in the iris stroma.

– Diffuse iris melanoma is less common and tends to produce acquired hyperchromic heterochromia with secondary glaucoma due to infiltration of the trabecular meshwork by tumor cells. It can affect the entire iris or only patches of its surface.

– Tapioca melanoma is a rare variant that presents characteristic translucent, fine nodules on the surface of the tumor resembling tapioca pudding.

– Trabecular meshwork melanoma affects the angle without the presence of a distinct mass, and it is usually associated with secondary ipsilateral glaucoma, which can cause a delay in diagnosis due to its resemblance to pigmentary glaucoma.

– Other less common presentations include spontaneous hyphema or iridocyclitis.

– Seeding of tumor cells on the iris surface or on the anterior chamber angle is a characteristic finding in many cases of iris melanoma. It is usually visualized as clumps of fine pigmented cells on slit-lamp exam or gonioscopy.

EPIDEMIOLOGY

Incidence

Iris melanoma represents <5% of all uveal melanomas. (Uveal melanoma has an estimated incidence of 6 cases per million per year in the US).

RISK FACTORS

• White race

• Inferior iris location (>80% of iris melanomas are located below the horizontal meridian of the iris)

• In an article by Territo and associates, the features that were associated with enlargement of the lesion included medial location of the mass on the iris and presence of pigment dispersion onto the adjacent iris and anterior chamber angle structures (3)[A]. Another article by Kliman and coworkers found a strong association between light iris color (blue, gray, or green) and the presence of iris melanocytic lesions (4)[A].

Genetics

• Iris melanomas can demonstrate monosomy, partial monosomy, or disomy of chromosome 3, 6, or 8 on genetic testing performed with microarray through fine needle aspiration biopsy (FNAB).

• These genetic features have been proven to be related to high risk (monosomy) or low risk (disomy) for systemic metastasis.

GENERAL PREVENTION

• Decrease sun exposure

• Periodic follow-up of suspicious iris lesions with ophthalmologist

PATHOPHYSIOLOGY

Malignant transformation of melanocytic iris stromal cells

ETIOLOGY

Unknown

COMMONLY ASSOCIATED CONDITIONS

• Unilateral secondary glaucoma

• Ocular melanocytosis

DIAGNOSIS

HISTORY

• Slow-growing pigmented or non-pigmented iris lesion (iris melanoma) noticed by the patient or the ophthalmologist on a routine eye visit

• Can be associated with pain or decreased vision in cases of iris melanoma with secondary glaucoma

PHYSICAL EXAM

• Secondary glaucoma with iris nevi is rare; therefore, elevated IOP should raise suspicion of malignancy. In a series of 169 patients with iris melanoma described by Shields and associates, the mean age at the time of diagnosis was 43 years, all patients were white, the mean tumor base was 6 mm, mean tumor thickness was 2 mm, the mean number of clock hours of tumor involvement in the iris as well as tumor seeding on the iris and on the anterior chamber angle was 4, and extraocular extension was present in 10 eyes (6%; ref. 5)[A].

• Other common features of iris melanoma are intrinsic and feeder vessels.

DIAGNOSTIC TESTS & INTERPRETATION

Lab

Initial lab tests

• Imaging tests include ultrasonographic biomicroscopy (UBM), anterior segment optical coherence tomography (AS-OCT), and anterior segment photography.

• Liver function tests, liver MRI, chest X-Ray, and complete physical exam

Imaging

Initial approach

• Slit-lamp examination and anterior segment photography

• IOP measurement

• Perform gonioscopy to assess angle involvement by tumor or seeds

• Perform transillumination to rule out ciliary body involvement

• UBM to measure thickness and to rule out associated ciliary body involvement or the presence of a cystic lesion

• AS-OCT can also be useful for imaging small, nonpigmented iris lesions, although it is limited by posterior shadowing in more pigmented, larger lesions

Follow-up & special considerations

• Follow-up every 6 months after treatment of iris melanoma to evaluate tumor regression and rule out recurrence

• Slit-lamp examination, anterior segment photography, UBM, gonioscopy, IOP measurement, and transillumination should be repeated at every visit.

• Systemic work up should be performed every 6 months lifelong to rule out the presence of systemic metastasis.

• Physical exam and liver function tests twice a year and liver MRI and chest X-Ray once a year, lifelong.

Diagnostic Procedures/Other

FNAB for cytology or cytogenetic analysis is a useful tool in the diagnosis of borderline iris lesions. The specimen should be interpreted by an experienced ophthalmic cytopathologist.

Pathological Findings

• Jakobiec and associates described the histopathologic features of 189 cases of excised iris melanomas and found that only 13% of them presented spindle B and epithelioid cells (6)[A].

• Some borderline cases of iris nevus are difficult to differentiate from low-grade iris melanoma, even for experienced pathologists.

DIFFERENTIAL DIAGNOSIS

• Iris nevus

• Iris melanocytoma

• Foreign body in the anterior chamber

• Irido-corneal endothelial (ICE) syndrome

• Iris lymphoma

• Iris pigment epithelium (IPE) cysts

• Adenoma (epithelioma) of the IPE

• Iris metastasis

• Iris granuloma

• Iris juvenile xanthogranuloma (JXG)

TREATMENT

MEDICATION

First Line

Currently, there are no effective medications for the treatment of iris melanoma.

Second Line

After surgical treatment, either with plaque brachytherapy or excision, atropine 1% once a day and Maxitrol (ointment) 3 times a day for a period of 6 weeks are prescribed to decrease inflammation, pain, and to avoid the formation of posterior synechiae.

• Bevacizumab (Avastin) 0.05 mg intravitreal or intracameral injection can be used in association with plaque radiotherapy or surgical excision, because iris melanoma was demonstrated to have vascular endothelial growth factor (VEGF) receptors according to reports from the ophthalmic literature.

ADDITIONAL TREATMENT

Issues for Referral

Glaucoma-filtering procedures such as trabeculectomy should be avoided because of the risk for spread of tumor cells outside the eye through the opening. A preferred method for lowering the IOP in these cases is through the use of glaucoma medications or laser cyclophotocoagulation.

SURGERY/OTHER PROCEDURES

• Lesions with unequivocal documented growth require treatment.

• Excisional biopsy (iridectomy, iridocyclectomy, or iridogoniocyclectomy for cases with concomitant ciliary body involvement) should be considered in circumscribed tumors, in the absence of seeds or elevated IOP.

• Plaque radiotherapy can be used to treat selected cases of unresectable iris melanoma or when the tumor is located in the patient’s only eye with useful vision. It can be used for larger tumors, those with a diffuse configuration, and in cases with tumor seeding in the anterior chamber or angle. Plaque is an alternative for eyes with iris melanoma in cases that would have been enucleated in the past (7)[A].

• Enucleation should be considered for diffuse tumors affecting more than half of the iris surface and trabecular meshwork, in cases with secondary glaucoma not responsive to IOP-lowering medications, diffuse tumor seeding into the anterior chamber and/or painful eye. Visual status of the contralateral eye should be assessed before proceeding with enucleation.

IN-PATIENT CONSIDERATIONS

Iris melanoma is managed on an outpatient basis.

ONGOING CARE

FOLLOW-UP RECOMMENDATIONS

Biannual eye evaluations including slit-lamp exam, gonioscopy, anterior segment photography, UBM, transillumination, and IOP measurement

Patient Monitoring

• In a report by Shields and associates, radiation-related complications after plaque brachytherapy for iris melanoma at 5-year follow-up included corneal epitheliopathy (9%), cataract (70%), and neovascular glaucoma (8%). After treatment, the incidence of elevated IOP at 5 years was 33%. Tumor recurrence was found in 8%, and enucleation was necessary in 13% at 5 years (7)[A].

• Systemic work up should include physical exam and liver function tests twice a year and MRI of the liver and chest X-ray once a year to rule out the presence of metastasis.

DIET

No dietary restrictions

PATIENT EDUCATION

Avoid excessive sun exposure

PROGNOSIS

In a recent retrospective study of 8033 cases of uveal melanoma, there were 285 iris melanoma cases. The authors found a rates of metastasis of 0.5%, 4%, and 7% at 3, 5, and 10 years, making this tumor less likely to metastasize than choroidal melanoma (8)[A].

• Metastases from iris melanoma are more common in older patients, patients with secondary glaucoma, extraocular extension, and angle involvement (risk factors; ref. 5)[A].

COMPLICATIONS

• Cataract formation after surgical treatment with either surgical resection or plaque radiotherapy

• Secondary glaucoma (more common in patients with seeding and angle involvement)

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