Retinocytoma: understanding pathogenesis, diagnosis, and treatment approaches

Abstract

Retinocytoma, or retinoma, is a rare benign intraocular tumor primarily affecting the retina. It is often considered a precursor or a differentiated form of retinoblastoma, a malignant retinal tumor predominantly seen in children. Despite its non-aggressive nature and excellent prognosis, retinocytoma remains a significant area of interest due to its implications for genetic counseling, early detection, and management of ocular tumors. The pathogenesis of retinocytoma is closely linked to mutations in the RB1 gene, which plays a vital role in regulating the cell cycle. The detection of RB1 mutations in peripheral blood indicates germline disease, substantially elevating the risk of bilateral retinoblastoma development. Despite its benign nature, retinocytoma necessitates vigilant monitoring due to its potential to transform into retinoblastoma. Current treatment strategies primarily focus on observation and regular follow-up. However, more aggressive treatments are considered if malignant transformation is suspected. The prognosis is generally favorable, with most patients maintaining good visual acuity and a low risk of progression to retinoblastoma. We aim to present an up-to-date review on epidemiology, clinical features, pathogenesis, macroscopic and histopathological features, diagnostic criteria, prognosis, and management strategies.

Keywords: RB1 gene; Immunohistochemistry; Ocular tumors.; Photoreceptor cells; Retinocytoma; Retinoma.

Fig. 1

Color fundus photograph of the right eye in a 30-year-old female, who was incidentally found to have a superonasal retinocytoma. The calcified tumor is endophytic, with surrounding patch of chorio-retinal atrophy

Fig. 2

B-scan ultrasonography of the right eye showing a retinocytoma mass with calcifications, exhibiting high internal reflectivity and associated shadowing

Fig. 3

Knudson’s two-hit hypothesis. If the first mutation is present in the germline, all somatic cells will carry one mutant allele. This increases the probability of a second mutation occurring during the somatic stage, which can affect multiple retinocytes in both eyes and other somatic precursor cells. If both mutations occur during the somatic stage, it leads to the development of unilateral unifocal retinoblastoma. Figure generated using BioRender

Fig. 4

Retinocytoma (Retinoma): Photoreceptor differentiation with numerous fleurettes (a, HE stain, original magnification 40x). Nuclear positivity for CRX (b, CRX, original magnification 20x). Negativity for Ki67 with a few reactive control cells (c, Ki67, original magnification 20x). Figure obtained with permission from Metz et al. (2017) [93]