Search for Distinctive Markers in DNT and Cortical Grade II Glioma in Children: Same Clinicopathological and Molecular Entities?

Background: Dysembryoplastic Neuroepithelial Tumours (DNT) are benign brain lesions arising during childhood that are characterized by early onset partial seizures, no neurological deficit and cortical location. Pathological diagnosis is easy when the glioneuronal element is present. Its absence might lead to the diagnosis of non-specific DNT or low-grade glioma (LGG). Objective: The aim of this retrospective study was to analyse clinicopathological and molecular features of a series of cortical tumours, in order to find diagnostic and prognostic markers to better custom treatment next. Methods: Twenty four children with cortical neuroepithelial tumour were included. Clinical and radiological data were collected. Histological diagnosis was reviewed for all patients. 1p19q and p53 status were obtained by FISH and immunohistochemistry respectively. IDH1-2 gene mutations were assessed by DNA sequencing. CGH-array was performed in 6/24 samples. Results: We recorded 13 DNT and 11 cortical LGG. Median age at surgery was 11.5 years. Overall survival was 100% and event-free survival at 10 years was 70%. No tumour displayed chromosomal alteration or 1p19q deletion or p53 expression. Only one patient with grade-II oligoastrocytoma had an IDH1 mutation. No statistical difference was found between the two populations in terms of age, sex, tumour location, type of surgical resection, disease progression and clinical status at last follow-up. Only the occurrence of septations on preoperative MRI was significantly associated with pathological features of DNT. Conclusion: Patients with DNT and cortical LGG share excellent outcome. Our genetic analysis could not distinguish DNT from LGG. In particular, CGH-array analysis was strictly normal in both tumor types. In attempt to find molecular markers, diagnosis of these lesions remains difficult when the glioneuronal element is lacking.