PURPOSE: To determine the size at which choroidal melanomas can metastasize and to report the characteristics of small fatal choroidal melanomas (SFCM).

DESIGN: Retrospective case series.

METHODS: Ten ocular oncology services submitted 45 patients with a choroidal melanoma 3 mm or less in thickness and 9 mm or less in largest basal diameter (LBD), when treated, who developed metastases.

RESULTS: Median tumor thickness was 2.4 mm (range, 1.0-3.0 mm) and LBD 7.3 mm (range, 3.0-9.0 mm). Of 14 (31%) tumors that were first observed, 12 grew a median of 0.5 mm (range, 0.1-1.2 mm) in thickness and 1.0 mm (range, 0-3.0 mm) in LBD within a median of 7 months; 3 were initially smaller than 3 mm in LBD. Number of risk factors for growth and metastasis was 0 for 4% of the tumors; 60% were over 2 mm in thickness, 63% had subretinal fluid, 84% caused symptoms, 57% had orange pigment, and 92% were within 3 mm of the disc. Local recurrence occurred in 8 of 31 eyes (26%) treated conservatively. Median metastasis-free survival was 4.5 years (range, 0.8-15.7 years). Kaplan-Meier estimate of metastasis developing was 15% (95% confidence interval [CI], 7-26), 51% (95% CI, 36-64) and 85% (95% CI, 71-92) by 2, 5, and 10 years, respectively. By the time of analysis, 37 patients had died of metastasis after a median of 7 months.

CONCLUSIONS: Choroidal melanomas less than 3.0 mm in LBD are highly unlikely to metastasize. Risk factors of an SFCM are similar to those for all choroidal melanomas of similar size.