Supplementary Material for: Retinocytoma: clinical and genetic characteristics in 16 pediatric and adult cases

Introduction: Retinocytomas are rare benign intraocular tumors that may mimic spontaneously regressed retinoblastoma.
Materials and Methods: Retrospective monocentric study of patients with retinocytoma in a French tertiary ocular oncology center, with an inclusion period from January 1999 to January 2024.
Results: Sixteen patients with retinocytoma were identified, and 1.351 retinoblastoma were diagnosed during the same 25-year period. Age at diagnosis ranged from 11 months to 75 years (mean 28.1 years). Thirteen cases were asymptomatic, while three presented with floaters, decreased visual acuity, or strabismus. Clinical presentation was a whitish or grayish retinal tumor with a translucent (87%) and/or fragmented appearance (76%) at diagnosis. A proportion of lesions were surrounded by atrophy (52%) and/or pigmentation (30%). Eleven patients had unilateral retinocytoma (one of which was multifocal), and five had bilateral lesions. Eight patients had a known family history of retinoblastoma. Patients were followed regularly and underwent genetic counseling. The eight patients with a family history had a germline pathogenic variation of the RB1 gene. None showed malignant transformation during follow-up (mean 79.5 months, median 35.5 months).
Conclusion: The presentation of retinocytoma is most often asymptomatic. Thus, diagnosis may be delayed to far later ages than expected with retinoblastoma. Retinocytoma may be associated with germline pathogenic variants of the RB1 gene, and follow-up is recommended due to rare but possible malignant transformation.