Bilateral retinoblastoma with ectopic intracranial retinoblastoma: trilateral retinoblastoma.

In 11 patients, bilateral retinoblastoma presented at a mean age of 6 months and pineoblastoma at 4 years. We suggest that the hereditary multicentric retinoblastoma arose in vestigeal photoreceptors in the pineal as well as in the hypothetical retinoblasts of the retina. In certain lower animals, the pineal functions as a photoreceptor organ, resembles the retina histologically, and is described as a "third eye." Hence, the patients we describe may be considered as having "trilateral retinoblastoma." Two possible variants of this entity were also noted: (1) three children without retinoblastoma with rosettes and photoreceptor differentiation characteristic of retinoblastoma, and (2) three additional cases involving children who presented with retinoblastoma-like tumors in the suprasellar or parasellar region 2 to 6 months before the discovery of intraocular retinoblastoma. These observations suggest that the retinoblastoma gene confers a previously unappreciated susceptibility to a narrow spectrum of neuroblastic tumors, which usually present in the retina but which can also occur ectopically.