Multifocal Retinocytoma Associated With Intronic Acceptor Splice Site Variants in the RB1 Gene

Retinocytomas are benign tumors that arise from mutations in the RB1 gene. Previous research describes the appearance of retinocytomas as that of treated retinoblastoma (Rb) lesions, with characteristics such as chorioretinal atrophy, calcification, and a lack of necrosis or mitotic activity on histopathology. We present the unusual case of an asymptomatic seven-year-old girl with two independent translucent masses in the peripheral retina of the right eye (OD) and extensive intraretinal tumor and vitreous seeds. Initial fundus examination and B-scan ultrasonography documented the two lesions with extensive placoid intraretinal tumor, uncalcified vitreous seeds, and an area of large subhyaloid seed on the optic nerve (ON) head. Given the clinical appearance and elevated intraocular pressure (IOP), the eye was staged as Group E and enucleated. Histopathology performed on the enucleated specimen revealed pure retinocytoma with two predominant retinal tumors, extensive flat intraretinal tumor, large subhyaloid seeds over the inner limiting membrane of the ON and focally central retina and localized uncalcified vitreous seeds with no malignant Rb component. A next-generation sequencing (NGS) panel detected two intronic acceptor splice site variants in the RB1 gene. While the previous literature documents cases of retinocytoma with vitreous seeds, this is the first case to our knowledge of a sporadic multifocal retinocytoma with a large ON prelimiting membrane, subhyaloid seeds, and vitreous seeds associated with two intronic acceptor splice site variants in the RB1 gene and no other detectable mutations.