Ultrasmall Gauge Biopsy of Small Choroidal Melanomas with a Subretinal Cannula

PURPOSE: To report a novel technique for biopsying small choroidal tumors for molecular prognostication utilizing a 38-gauge subretinal cannula. METHODS: Through a transvitreal approach, a subretinal cannula enters the eye and penetrates the tumor in an area devoid of blood vessels. Manual aspiration is conducted with the aid of a surgical assistant. The cannula's transparency allows for visualization of biopsy depth and tissue aspiration. The cannula is withdrawn, and the sample is manually injected into the specimen vial. RESULTS: Sixteen patients underwent biopsy using this technique for suspected small choroidal melanoma (1.5 mm average thickness). Sufficient diagnostic yield was appreciated in 88% (14/16) of patients. Six of 16 patients consisted of subfoveal tumors. Of 2 patients without yield, there was a technical processing error and an anteriorly located tumor. No complications were observed. CONCLUSION: The described technique using a subretinal cannula for choroidal tumor biopsy yields sufficient specimen for molecular analysis while potentially minimizing visually threatening side effects. It may hold additional benefit when biopsying small, posterior tumors, which are adjacent to sensitive anatomy.