A review of the large published series of patients with retinocytoma suggests that second malignant neoplasms are rare in patients with retinocytoma [1, 4, 8, 23]. It is possible that mechanisms that play a protective role in inducing retinocytoma also protect the extraocular cells from the development of second malignant neoplasms [24, 25].

Retinocytoma is considered to be a benign counterpart of retinoblastoma (Fig. 7.2) [2, 4, 7, 10]. The majority of retinocytomas are diagnosed when the parents of a child who has retinoblastoma are examined [1, 4, 8]. The examination of first-degree relatives, especially parents, when a new case of retinoblastoma is diagnosed is extremely important as it has major implications in genetic counseling [26]. The occurrences of retinoblastoma and retinocytoma are not mutually exclusive. In fact, retinoblastoma is now thought to be the final malignant result on a continuum of clonal progression from normal to benign to malignant cells after loss of RB1 [12–14].

Histopathologic analysis of eyes enucleated for retinoblastoma reveals the presence of retinocytoma or retinoma adjacent to both normal retina and in up to 16 % of retinoblastoma tumors [12]. It comes as no surprise then that retinocytoma or retinoma and retinoblastoma can coexist as two separate tumors in the same eye [20] or between two eyes of the same patient [1, 4]. While many retinocytomas or retinomas remain benign for the lifetime of an individual, malignant transformation into retinoblastoma is well known [9, 27] and perhaps such occurrences account for cases of retinoblastoma in adults [28, 29].

Another scenario when diagnosis of retinocytoma can be retrospectively considered is when there is minimal initial response to chemotherapy in tumors presumed to be retinoblastoma. Moreover, the residual tumors fail to grow when all treatment has been discontinued. It is postulated that lack of response to chemotherapy is indicative of extreme differentiation (retinocytoma) rather than chemoresistance by an aggressive tumor [30].

In the majority of cases, the diagnosis of retinocytoma can be made with indirect ophthalmoscopy. However, fluorescein angiography, ultrasonography, and optical coherence tomography (OCT) can be useful ancillary studies.

Despite characteristic ophthalmoscopic features of retinocytoma outlined above, certain entities can closely resemble retinocytoma. Retinoblastoma, astrocytic hamartoma, and myelinated nerve fibers can be difficult to differentiate ophthalmoscopically from retinocytoma (Table 7.1).