Choroidal melanomas smaller than 3 mm unlikely to metastasize

This retrospective study reports the size of choroidal melanomas that metastasize and characteristics of small fatal choroidal melanoma.

Study design

Researchers examined 45 patients who developed metastatic disease from a uveal melanoma tumor that was 3 mm or less in thickness and 9 mm or less in the largest basal diameter (LBD). Patients were diagnosed between 1962 and 2010.

Outcomes

The median tumor thickness and LBD was 2.4 mm and 7.3 mm, respectively. The 4 smallest tumors had an LBD ranging from 3 to 5 mm. Fourteen eyes were enucleated initially and 31 were treated with globe conserving therapy (brachytherapy or proton beam). Fourteen tumors were observed before treatment. Local recurrence was observed in 8 of the 31 eyes treated conservatively (26%). Melanomas less than 3 mm did not metastasize. Risk factors for choroidal melanoma were consistent with previous studies and included thickness greater than 2 mm, subretinal fluid, symptoms, orange pigment, and margin within 2-disc diameters of the optic disc.

During follow-up, 37 patients died due to metastatic disease. The median survival was 6 years (range 1.6–16.7 years) from primary treatment. Patients survived an average of 8 months after developing systemic metastases.

Limitations

The recurrence rate in this study (26%) was much higher than normally observed with globe conserving therapy. Although the reason is unclear, it may be due to the difficulty treating tumors of this size. It is not clear if recurrence led to a higher risk of metastasis in this study.

Clinical significance

This study, which spanned 48 years, found that choroidal melanomas less than 3 mm in LBD did not develop into metastatic disease. The findings suggest that choroidal lesions of this size may be safely observed for growth without increasing the risk of metastasis.