Optical coherence tomography angiography in choroidal melanoma and nevus

Synopsis In optical coherence tomography angiography, the choroidal vascular flow rate in choroidal melanoma is significantly lower than that in choroidal nevus. Objective The objective of this study was to describe the choriocapillaris and retinal features imaged by optical coherence tomography angiography (OCTA) in eyes with choroidal nevus from small malignant choroidal melanoma. Methods In this retrospective, noninvasive, observational study, 11 patients diagnosed with small choroidal mass (five with choroidal nevus and six with malignant melanoma) who underwent dilated fundus examination, ocular ultrasonography and OCTA images were compared. Results In choroidal nevus of all patients, OCTA demonstrated a hyporeflective mass with no significant deformity of choroidal vasculature and an intact retinal pigment epithelium (RPE)-Bruch's membrane complex. The flow void mass was surrounded by an intense vascular rim named as surface microvasculature (SMV) that had an approximately similar flow rate median of 63.68 mm2 (60.42-67.62 mm2), comparable with the median of the contralateral normal eye of 61.77 mm2 (60.42-64.53 mm2; P>0.09) for nevi. OCTA showed an obscured Bruch's membrane-RPE-Bruch's membrane complex and outer retinal layer in choroidal melanomas. Choriocapillaris flow rate over the melanomas was 55.73% (41.93%-60.82%), and the corresponding normal areas had a flow area of 62.75% (61.99%-63.10%; P=0.01). A flow rate difference between choroidal melanoma and nevus was significant (P=0.006). Axial and peripheral feeding vessels were more dilated and tortuous compared with benign nevi. Conclusion Decreased flow rate of SMV of choroidal melanoma cases compared with nevi was a significant finding. Detection of characteristic vascular features of choroidal melanoma by OCTA could make OCTA an assuring diagnostic modality to differentiate malignant lesions.