[Optical coherence tomography angiography features of choroidal melanotic tumors]

Objective: To describe and compare the internal vascular features of choroidal melanoma (CM) and choroidal nevus on optical coherence tomography angiography (OCTA). Methods: This cross-sectional study included patients clinically diagnosed with CM or choroidal nevus at Beijing Tongren Hospital between July 2019 and March 2025. Tumor-centered OCTA images were acquired, and the intrinsic tumor vasculature was reconstructed on two en face planes, the choriocapillaris slab and the full-thickness choroid slab. The malignant transformation risk of choroidal nevus was assessed using the multimodal imaging-based TFSOM-DIM criteria. Nevi with two or more high-risk features were classified as high-risk nevi, and the OCTA features of high and low-risk nevi was analyzed. The OCTA features were compared between the CM and nevus groups using the χ² test or Fisher's exact test. Results: A total of 95 eyes (95 patients) were included, consisting of 49 right eyes and 46 left eyes. There were 45 males (47.4%) and 50 females (52.6%), with a mean age of (47.6±14.1) years. All patients had unilateral involvement. The CM group included 67 patients (67 eyes), with 35 right eyes and 32 left eyes, comprising 36 males (53.7%) and 31 females (46.3%), with a mean age of (47.1±14.3) years. The choroidal nevus group included 28 patients (28 eyes), with 14 right eyes and 14 left eyes, consisting of 9 males (32.1%) and 19 females (67.9%), with a mean age of 48.8±13.6 years. There were no significant differences between the two groups in eye laterality (χ²=0.04, P=0.842), age (t=0.53, P=0.299), or sex distribution (χ²=3.69, P=0.055). In the choroid en face slab, disorganized vascular networks and vascular loops were observed in 66 CM cases (98.5%) and 14 nevus cases (50.0%; χ²=34.95, P<0.001). In the choriocapillaris en face slab, patchy avascular areas were detected in 54 CM cases (80.6%) and 9 nevi (32.1%; χ²=20.79, P<0.001), while the intrinsic tumor vasculature was present in 52 CM cases (77.6%) and 8 nevi (28.6%; χ²=20.41, P<0.001). Two distinct vascular patterns were identified within choroidal nevi on the choroid slab: 14 nevi (50.0%) exhibited diffusely attenuated flow signals without identifiable tumor vasculature, whereas the other 14 nevi (50.0%) demonstrated melanoma-like disorganized vascular networks. Among 17 low-risk and 11 high-risk nevi, melanoma-like disorganized vascular networks were present in 9 low-risk nevi (29.4%) and 5 high-risk nevi (81.8%), with a statistically significant difference (χ²=7.34, P=0.018). Conclusion: In OCTA images, CMs and choroidal nevi exhibit different internal vascular networks. CMs typically exhibit disorganized vasculature with vascular networks and loops, whereas choroidal nevi more often show attenuated flow signals or finer, more orderly vascular structures. The presence of melanoma-like disorganized vascular networks in choroidal nevi may significantly predict malignant transformation and serve as an imaging indicator for identifying high-risk nevi.