Clinical and Pathologic Characteristics of Biopsy-proven Iris Melanoma: a Multicenter International Study

Objective: To collaborate with multiple centers to identify representative epidemiological, clinical, and pathologic characteristics of melanoma of the iris. This international, multicenter, Internet-assisted study in ophthalmic oncology demonstrates the collaboration among eye cancer specialists to stage and describe the clinical and pathologic characteristics of biopsy-proven melanoma of the iris.

Methods: A computer program was created to allow for Internet-assisted multicenter, privacy-protected, online data entry. Eight eye cancer centers in 6 countries performed retrospective chart reviews. Statistical analysis included patient and tumor characteristics, ocular and angle abnormalities, management, histopathology, and outcomes.

Results: A total of 131 patients with iris melanoma (mean age, 64 years [range, 20-100 years]) were found to have blue-gray (62.2%), green-hazel (29.1%), or brown (8.7%) irides. Iris melanoma color was brown (65.6%), amelanotic (9.9%), and multicolored (6.9%). A mean of 2.5 clock hours of iris was visibly involved with melanoma, typically centered at the 6-o'clock meridian. Presentations included iritis, glaucoma, hyphema, and sector cataract. High-frequency ultrasonography revealed a largest mean tumor diameter of 4.9 mm, a mean maximum tumor thickness of 1.9 mm, angle blunting (52%), iris root disinsertion (9%), and posterior iris pigment epithelium displacement (9%). Using the American Joint Commission on Cancer-International Union Against Cancer classification, we identified 56% of tumors as T1, 34% of tumors as T2, 2% of tumors as T3, and 1% of tumors as T4. Histopathologic grades were G1-spindle (54%), G2-mixed (28%), G3-epithelioid (5%), and undetermined (13%) cell types. Primary treatment involved radiation (26%) and surgery (64%). Kaplan-Meier analysis found a 10.7% risk of metastatic melanoma at 5 years.

Conclusions: Iris melanomas were most likely to be brown and found in the inferior quadrants of patients with light irides. Typically small and unifocal, melanomas are commonly associated with angle blunting and spindle cell histopathology. This multicenter, Internet-based, international study successfully pooled data and extracted information on biopsy-proven melanoma of the iris.