Presumed Ectopic Trilateral Retinoblastoma: Case Report

Introduction

Retinoblastoma (rb) is the most frequent intraocular tumor, occurring in 1 : 17 000 live births and accounting for 6% of all pediatric cancers under the age of 5 [1]. The disease can affect one or both eyes and is caused by a somatic or a germline mutation in the RB1 gene, a tumor suppressor gene located on the long arm of chromosome 13 (13q14) [1]. Children with heritable forms have a 3.5% risk of developing an intracranial midline primitive neuroectodermal tumor, usually located in the pineal gland (73 – 83% of cases) [2] – [4] or the suprasellar/parasellar region (11 – 22% of cases) [2], [4], [5], a condition known as trilateral retinoblastoma (Trb). Unusual locations with proven histopathology such as the third or fourth ventricle or the cerebellum (1%) [3], [5] have also been reported in isolated cases. Magnetic resonance imaging (1.5 or 3 Tesla MRI) is usually recommended for all rb cases at baseline, with a minimum annual examination for germline carriers until 3 to 5 years of age for the early detection of metachronous asymptomatic Trb. Carriers of a germline RB1 mutation are also at a lifetime risk of developing various types of secondary primary neoplasms (SPNs), especially if treated with external beam irradiation [1].

Management and outcome of rb patients depend greatly on the disease extent at presentation and access to a specialized center for ocular oncology. In high-income countries, where metastatic disease at presentation is rare, rb has 5-year disease-free survival rates of 97 – 99% [1]. Treatment of intraocular disease includes chemotherapy (intra-arterial, intravenous, and/or intraocular), focal treatments such as thermotherapy or cryotherapy, plaque brachytherapy, and/or enucleation. Despite progress made over the last decades, the outcome of metastatic disease, especially in cases of central nervous system (CNS) involvement, remains poor [1].

Herein, we report an atypical case of optic nerve sheath lesion in a child with bilateral rb, presumed to be an ectopic Trb, and discuss the differential diagnosis. Informed consent for publication was obtained from the patientʼs legal guardian.

Publication History

Received: 27 October 2024

Accepted: 04 December 2024

Article published online:
05 March 2025

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