Rhabdoid component emerging as a subclonal evolution of paediatric glioneuronal tumours

AimsOur study aimed to expand the knowledge of a rare entity: glioma with a rhabdoid component (RC).MethodsWe collected French pediatric patients u003c 18 years presenting a glioma harboring a RC, either at diagnosis or during evolution. We described clinical, pathological and genetic data.ResultsWe report 4 further cases of supratentorial pediatric patients presenting glioneuronal tumor with a RC and homozygous deletion of SMARCB1 either at diagnosis or during evolution. Age at diagnosis ranged from 13 months to 9 years. All tumors were located in the fronto-parietal region. Histology of the glioneuronal component (GC) was ganglioglioma (n=2), a pleomorphic xanthoastrocytoma, and an unclassifiable glioneuronal tumor. The RC was evidenced at diagnosis for all patients. All cells in the RC showed a BAF47 loss of expression in contrary to the GC component. In two patients, array-CGH from the GC and the RC clearly showed similar profiles. However, SMARCB1 deletion was hemizygous in GC and homozygous in RC, suggesting that RC was a subclonal evolution of GC. BRAF V600E mutation was found in one case, suggesting that this underlying mutation is inconstant and not required to the malignant evolution. Overall 2 patients remain in complete remission 2 years and 5 years after the initial diagnosis and after a highly intensive treatment.ConclusionThis short series brings evidence that a subset of pediatric glioneuronal tumors may secondarily transform into rhabdoid tumors. CGH-profiling of the GC shows a hemizygous SMARCB1 deletion that may underline potential aggressive transformation of such benign tumors.This article is protected by copyright. All rights reserved.