Multifocal Intraretinal Tumour Deposits following Treatment of an Ipsilateral Choroidal Melanoma

Background/Aims: The aim of this study was to report a patient who, following plaque brachytherapy for a choroidal melanoma, developed two separate retinal foci of malignant melanoma in the same eye, and suggest possible mechanisms that might explain such an occurrence. Methods: We conducted a retrospective case report. Results: A 79-year-old Caucasian male developed a left inferotemporal choroidal melanoma in 2016 and subsequently underwent ruthenium-106 plaque brachytherapy under the care of the Scottish Ocular Oncology Service. Serial B-scan ultrasonography demonstrated a post-treatment reduction in tumour height to <2 mm. In 2018, 27 months after the treatment, the patient complained of a "black spot" in the centre of his left eye vision. His visual acuity had reduced to counting fingers from 6/24 (corrected Snellen visual acuity). Several new areas of pigmentation and elevation were observed, and uveal melanoma recurrence was initially suspected. Given the multifocal nature of the presentation, the multi-disciplinary team recommended enucleation. Histological examination of the enucleated eye revealed three discrete foci of malignant melanoma - the previously treated choroidal malignant melanoma, and two solitary deposits of malignant melanoma within the retina. Conclusion: Retinoinvasive melanoma is a rare subtype of uveal melanoma, characterised by transvitreal melanoma invasion of the retina at a site non-contiguous with the uveal tumour, which may explain the clinical and pathological findings of the reported case.