Angiographic Features of Iris Melanocytic Tumors: Nevus versus Melanoma

Determining the nature of iris melanocytic tumors based on clinical exam alone remains challenging. Tumor-associated vasculature of iris melanocytic lesions may facilitate the ability to discern between iris nevus and melanoma.

In a single-institution, retrospective, observational study of 45 patients with pathologically confirmed iris melanoma and 15 patients with iris nevi that were either clinically stable or pathologically confirmed were included. Tumor characteristics and associated vasculature were identified on clinical exam and slit-lamp photographs. Fluorescein angiographic parameters including feeder vessels, intrinsic vessels, leakage, masking, and angiographic silence were assessed.

Feeder vessels were present in 17 (43%) melanomas and were absent in the nevus group (p = 0.002). Thirty-three (83%) iris melanomas and 5 (33%) iris nevi were observed to have intrinsic vessels, and a statistically significant association of intrinsic vessels with malignancy (p = 0.001) was noted. Fluorescein leakage was also observed more frequently in iris melanoma 39 (98%) than in nevi 9 (60) with a significant difference (p = 0.001). Angiographic silence occurred in 3 nevi (20%) and was not observed in any melanoma (p = 0.017). Overall, the presence of intrinsic vessels +/- feeder vessels had high sensitivity (0.85) and high positive predictive value (0.87) for diagnosis of iris melanoma.

Anterior segment fluorescein angiography allows for the assessment of tumor-associated vascular patterns and demonstrates utility in differentiating iris nevi from melanoma. Feeder vessels were only observed in iris melanoma and were absent in iris nevi. The intrinsic vessels were present more frequently in melanomas and are thus associated with malignancy. Angiographic silence is indicative of iris nevi.