TRILATERAL RETINOBLASTOMA - INSIGHTS INTO HISTOGENESIS AND MANAGEMENT

Trilateral retinoblastoma (TRb) is a syndrome involving midline intrac ranial malignancies in children with the heritable form of retinoblast oma. All cases of TRb reported from 1971 to 1997 were reviewed. The hi stopathologic findings, clinical features, treatment modalities, and s urvival rates from 80 cases were evaluated. Histopathologic findings f rom intracranial malignancies demonstrated primitive neuroectodermal t umors in 61.5% of cases. Various degrees of neuronal or photoreceptor differentiation were seen in the other 38.5% of cases. Autopsy, histop athologic, and radiologic examinations did not show a more definitive site of origin of these intracranial tumors, although ''pinealoblastom a'' was often the diagnosis reported. These findings, together with an alysis of the histopathologic similarities among human primitive neuro ectodermal tumors, pinealoblastoma, retinoblastoma, and ependy-moblast oma, suggest that TRb more likely arises from a germinal layer of pred isposed primitive subependymal neuroblasts that are not necessarily de stined for pineal or photoreceptor differentiation. Trilateral tumors have also been found in transgenic mice expressing the simian virus 40 T-antigen. Transgenic murine intracranial tumors are primitive neuroe ctodermal tumors arising from the subependymal layer. Transgenic mice with the murine interphotoreceptor cell binding protein promoter and s imian virus 40 T-antigen also develop pineal tumors. Trilateral retino blastoma is usually fatal, with an average survival time of 11.2 month s. Therapies include radiation, systemic chemotherapy, intrathecal che motherapy, and surgical resection/craniotomy in combination with radia tion and/or chemotherapy. Survival may be prolonged with combination c hemotherapy (24.6 months) and if neuroradiologic screening identifies TRb before symptoms are present (23.5 months). Recent success with pla tinum-based chemoreduction of intraocular retinoblastoma may indicate a similar role for platinum-based chemotherapy in the treatment of TRb . Routine central nervous system imaging should be considered in the m anagement of TRb. (Surv Ophthalmol 43:59-70, 1998. (C) 1998 by Elsevie r Science Inc. All rights reserved.).