Malignant Transformation of a Choroidal Nevus

Choroidal nevus is the most common intraocular tumor, and most cases are benign and have no symptoms. However, choroidal nevus carries a low risk for transformation into melanoma, which is a highly aggressive and deadly cancer. In this case report, we present a male patient with blurred vision in his left eye for six months. Multimodal fundus imaging reported a large pigmented gray-brown choroidal lesion adjacent to the optic disc in his left eye, along with intraretinal and subretinal fluid (SRF) accumulation involving the macula and fluorescein leakage. Choroidal nevus was then diagnosed, and bevacizumab was given by intravitreal injection. After one month of bevacizumab treatment, spectral-domain optical coherence tomography showed a decrease in SRF. After four months of bevacizumab treatment, the patient suffered from more SRF and an elevated lesion in his left eye. During subsequent follow-up, the lesion continued to increase in size. Given the possibility of a malignant transformation of choroidal nevus into melanoma, transpupillary thermotherapy (TTT) was performed. The choroidal melanoma appeared to be necrotic at 10 months post-TTT. The patient's left eye was enucleated due to neovascular glaucoma 17 months post-TTT. Histopathologic examination showed diffuse infiltration of melanoma cells in the retina, choroid and optic nerve, and cell growth on the surface of the optic nerve papilla. Multiple treatment modalities, including external beam radiotherapy and systemic chemotherapy, were applied, but the patient eventually died due to metastasis. Patients with choroidal nevus should be managed with multimodal fundus imaging and be closely followed up due to the risk of transformation into a malignant melanoma. For cases with clinical and imaging features of malignant transformation, early intervention and long-term follow-up are required to achieve local disease control and vision preservation.