The retinocytoma is a rare, benign form of retinal tumor related to the retinoblastoma. Like retinoblastomas, retinocytomas arise from a mutation in the RB1 gene.

The retinocytoma should be differentiated from the classically described regressed retinoblastoma that occurs in a phthisical eye, and which consists of ghost-like remnants of necrotic tumor cells that are embedded within a partially calcified matrix of basophilic material. They have a translucent “fish flesh” appearance, contain abundant calcification that has been likened to cottage cheese, and are surrounded by a ring of retinal pigment epithelium depigmentation.

This tumor can manifest as spontaneously regressed retinoblastoma, can follow treatment of retinoblastomas, or can be seen in untreated tumors.