Several conditions can resemble retinoblastoma by causing a white fundus lesion and/or by causing leukocoria (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24-25). The clinician should be familiar with these conditions and the features that serve to differentiate them clinically from retinoblastoma. Many simulating lesions are other tumors, like astrocytic hamartoma, medulloepithelioma, and combined hamartoma, and they are covered mainly in other chapters; they are briefly mentioned here in the context of their similarities to retinoblastoma. This chapter describes primarily some nonneoplastic conditions that can simulate retinoblastoma. These conditions are classified as follows:

This comprehensive list does not reflect the frequency of these lesions in a clinical practice. In a series of 500 patients referred with the diagnosis of possible retinoblastoma, 288 proved on subsequent evaluation to have retinoblastoma and 212 proved to have simulating lesions (3,4). The three conditions that most closely simulated retinoblastoma were persistent hyperplastic primary vitreous (PHPV) (28%), Coats disease (16%), and inflammation, usually ocular toxocariasis (16%). Since the publication of those articles, Coats disease has passed PHPV as the most frequent pseudoretinoblastoma, and ocular toxocariasis has become much less frequent in our practice. The specific clinical features that help to differentiate these conditions are discussed in detail in the literature (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23) and are summarized in the following plates.