Choroidal Melanoma Simulating Adenoma of the Retinal Pigment Epithelium Arising at the Site of Congenital Hypertrophy of the Retinal Pigment Epithelium

Neoplasms of the retinal pigment epithelium (RPE) are rare tumors that can simulate choroidal melanoma, but clinical and imaging characteristics often differentiate these lesions. We report a 70-year-old male with an abruptly elevated pigmented lesion that arose at the site of congenital hypertrophy of the RPE and demonstrated associated exudation, as well as feeding and draining vessels, suggestive of RPE adenoma. Optical coherence tomography showed retinal elevation with serous retinal detachment adjacent to the mass, and ultrasonography revealed an abruptly elevated, moderately echodense mass of 6.4-mm thickness. Fluorescein ­angiography showed early tumor hypofluorescence, late ­tumor hyperfluorescence with staining and leakage, and ­retinal vessels buried under the mass, suggestive of a retinal tumor. The patient was monitored with the presumed diagnosis of RPE adenoma, but 3 months later, the growth was documented and fine-needle aspiration biopsy revealed choroidal melanoma. Management with I-125 plaque radiotherapy was performed leading to tumor regression and a thickness of 4.6 mm.