4. Retinoblastoma: Epidemiologic Aspects

Retinoblastoma is the paradigm for the two-hit model of carcinogenesis [1]. From a genetic standpoint, three forms may be considered: familial, sporadic heritable, and nonheritable retinoblastoma (Fig. 4.1). These three forms are thought to account for most instances of retinoblastoma. However, findings on imprinting and mosaicism indicate that our understanding of the genetics of this disease is still evolving and that the genetics are more complex than indicated by our discussion of the three main forms [2–5]. In the discussion that follows, we use the proportions of retinoblastomas of each form seen in industrialized countries. In developing countries, nonheritable retinoblastoma accounts for a larger proportion.