Objective  To determine the rate of metastasis of uveal melanoma on the basis of tumor thickness in millimeters.

Methods  Retrospective medical record review.

Results  The mean (median) patient age was 58 (59) years. A total of 8033 eyes were examined. Of the 285 eyes with iris melanoma, the mean tumor thickness was 2.7 mm and metastasis occurred in 0.5%, 4%, and 7% at 3, 5, and 10 years, respectively. Of the 492 eyes with ciliary body melanoma, the mean tumor thickness was 6.6 mm and metastasis occurred in 12%, 19%, and 33% at 3, 5, and 10 years, respectively. Of the 7256 eyes with choroidal melanoma, the mean tumor thickness was 5.5 mm and metastasis occurred in 8%, 15%, and 25% at 3, 5, and 10 years, respectively. For all uveal melanoma, metastasis at 5, 10, and 20 years was 6%, 12%, and 20% for small melanoma (0-3.0 mm thickness), 14%, 26%, and 37% for medium melanoma (3.1-8.0 mm), and 35%, 49%, and 67% for large melanoma (>8.0 mm). More specifically, metastasis per millimeter increment at 10 years was 6% (0-1.0 mm thickness), 12% (1.1-2.0 mm), 12% (2.1-3.0 mm), 16% (3.1-4.0 mm), 27% (4.1-5.0 mm), 28% (5.1-6.0 mm), 29% (6.1-7.0 mm), 41% (7.1-8.0 mm), 50% (8.1-9.0 mm), 44% (9.1-10.0 mm), and 51% (>10.0 mm). Clinical factors predictive of metastasis by multivariate analysis included increasing patient age, ciliary body location, increasing tumor diameter, increasing tumor thickness, having a brown tumor, and the presence of subretinal fluid, intraocular hemorrhage, or extraocular extension.

Conclusion  Increasing millimeter thickness of uveal melanoma is associated with increasing risk for metastasis.