Retinocytoma or Retinoma

The term retinoma was first introduced in 1982 by Gallie et al. to define nonprogressive retinal lesions observed in patients known to carry the genetic variant of retinoblastoma. Based on the nomenclature used to classify pineal body tumors (benign, pineocytoma, and malignant, pineoblastoma), an alternate term, retinocytoma, has also been used to describe these tumors. The incidence of retinocytoma in the general population is not known but ranges from 1.8% to 10% among those diagnosed with or having a positive family history of retinoblastoma. Most of the cases are diagnosed in the parents or other first-degree relatives of a child with retinoblastoma. Retinocytoma is considered to be a benign manifestation of the RB1 gene mutation. In theory, then, all retinoblastomas progress through a stage of retinocytoma, however brief, before accrued genetic instability leads to uncontrolled proliferation (retinoblastoma). The majority of patients with retinocytoma are asymptomatic, and the diagnosis occurs either on routine eye examination or when the diagnosis of retinoblastoma is made in another family member, prompting an eye examination. The ophthalmoscopic appearance of the retinocytoma resembles the spectrum of retinoblastoma regression patterns observed after irradiation. The presence of a translucent-gray retinal mass, calcification, retinal pigment epithelial alteration, and chorioretinal atrophy are four diagnostic ophthalmoscopic features of retinocytoma. Hematoxylin and eosin of retinocytoma show well-differentiated prominent photoreceptors (fleurettes) with normal-sized nuclei with no pleomorphism or mitotic activity. Despite the characteristic ophthalmoscopic features of retinocytoma outlined above, certain entities such as retinoblastoma, astrocytic hamartoma, and myelinated nerve fibers can closely resemble retinocytoma. While many retinocytomas remain benign for the lifetime of an individual, malignant transformation into retinoblastoma can also occur with an estimated transformation rate of 4%. Thus, if suspected, retinocytoma should initially be closely followed, especially in children, to confirm the absence of growth.