Landscape of chromosomal copy number aberrations in gangliogliomas and dysembryoplastic neuroepithelial tumours

Aim: Gangliogliomas (GGs) and dysembryoplastic neuroepithelial tumours (DNTs) represent the most common histological entities within the spectrum of glioneuronal tumours (GNTs). The wide variability of morphological features complicates histological classification, including discrimination from prognostically distinct diffuse low-grade astrocytomas (AIIs). This study was performed to increase our understanding of these tumours. Methods: We studied chromosomal copy number aberrations(CNAs) by genome-wide sequencing in a large cohort of GNTs and linked these to comprehensive histological analysis and clinical characteristics. One hundred fourteen GNTs were studied: 50GGs and 64DNTs. Also, a data set of CNAs from 38 diffuse AIIs was included. Results: The most frequent CNAs in both GGs and DNTs were gains at chromosomes 5 and 7, often concurrent, and gain at chromosome 6. None of the CNAs was linked to histological subtype, immunohistochemical features or to clinical characteristics. Comparison of AIIs and diffuse GNTs revealed that gain at whole chromosome 5 is only observed in GNTs. CNA patterns indicative of chromothripsis were detected in three GNTs. Conclusion: We conclude that GNTs with diverse morphologies share molecular features, and our findings support the need to improve classification and differential diagnosis of tumour entities within the spectrum of GNTs, as well as their distinction from other gliomas.