Baseline central nervous system magnetic resonance imaging in early detection of trilateral retinoblastoma: pitfalls in the diagnosis of pineal gland lesions

Background: Trilateral retinoblastoma (TRB) is a rare disease associating bilateral retinoblastoma (RB) with primitive intracranial neuroblastic tumor.

Aim: To verify the occurrence of TRB in a single-Center case series and point out the clinical relevance of a baseline brain magnetic resonance imaging (MRI) in RB, focusing on pineal gland lesions.

Patients and methods: Baseline MRI was routinely performed in all cases of RB from 1999. All MRIs were reviewed for this study and the RB database was checked in order to identify patients characteristics, treatments and follow-up.

Results: A total of 107 patients with RB were diagnosed between 1999 and 2012. Sixty-two patients had unilateral RB and 45 bilateral RB. MRI revealed the presence of pineal gland lesions in 10 patients (9%); seven were considered pineal benign cysts (6.5%), while in three patients (2.8%), TRB was suspected. All patients with TRB presented hereditary RB. In one patient, the suspected TRB was metachronous and in the other two patients was synchronous. Biopsy was not performed. Cerobrospinal fluid (CSF) was negative in all patients. The MRI modification, before treatment in the first case and later in the second case, confirmed the TRB diagnosis. The third patient died due to progressive Central Nervous System (CNS) disease that clearly confirmed the TRB diagnosis. None of the three patients had received prior chemotherapeutic treatment.

Discussion: TRB represents a rare condition in this series, occurring in three (2.8%) out of all patients with RB. A synchronous presentation with small lesion seems more frequent when a baseline MRI is performed. When a histologically-proven diagnosis is not available, a suspected diagnosis should be considered with caution and only follow-up will confirm the diagnosis. A wait-and-see approach should be considered.