ABSTRACT
BACKGROUND AND PURPOSE: CNS embryonal tumor with PLAGL1/PLAGL2 amplification (ET, PLAGL) is a newly identified, highly malignant pediatric tumor. Systematic MRI descriptions of ET, PLAGL are currently lacking. MATERIALS AND METHODS: MRI data from 19 treatment-naïve patients with confirmed ET, PLAGL were analyzed. Evaluation focused on anatomical involvement, tumor localization, MRI signal characteristics, DWI behavior, and the presence of necrosis and hemorrhage. Descriptive statistics (median, interquartile range, percentage) were assessed. RESULTS: Ten patients had PLAGL1 and nine PLAGL2 amplifications. The solid components of the tumors were often multinodular with heterogeneous enhancement (mild to intermediate in 47% and intermediate to strong in 47% of cases). Non-solid components included cysts in 47% and necrosis in 84% of the cases. The tumors showed heterogeneous T2WI hyper-and isointensity (74%), relatively little diffusion restriction (ADC values < contralateral normal-appearing WM in 36% of cases with available DWI), and tendencies towards hemorrhage/calcification (42%). No reliable distinction was found between PLAGL1-and PLAGL2-amplified tumors or compared to other embryonal CNS tumors. CONCLUSIONS: The study contributes to understanding the imaging characteristics of ET, PLAGL. It underscores the need for collaboration in studying rare pediatric tumors and advocates for the use of harmonized imaging protocols for better characterization. ABBREVIATIONS: ATRT= atypical teratoid/rhabdoid tumor; ETMR= embryonal tumor with multilayered rosettes; ET, PLAGL= CNS embryonal tumor with PLAGL amplification; EVD= external ventricular drain; IQR: interquartile range; PLAGL1= pleomorphic adenoma gene-like 1; PLAGL2= pleomorphic adenoma gene-like 2; WHO= World Health Organization.
ABSTRACT
Low-grade epilepsy-associated brain tumours (LEAT) are the second most common cause for drug-resistant, focal epilepsy, that is ganglioglioma (GG) and dysembryoplastic neuroepithelial tumours (DNT). However, molecular pathogenesis, risk factors for malignant progression and their frequent association with drug-resistant focal seizures remain poorly understood. This contrasts recent progress in understanding the molecular-genetic basis and targeted treatment options in diffuse gliomas. The Neuropathology Task Force of the International League Against Epilepsy examined available literature to identify common obstacles in diagnosis and research of LEAT. Analysis of 10 published tumour series from epilepsy surgery pointed to poor inter-rater agreement for the histopathology diagnosis. The Task Force tested this hypothesis using a web-based microscopy agreement study. In a series of 30 LEAT, 25 raters from 18 countries agreed in only 40% of cases. Highest discordance in microscopic diagnosis occurred between GG and DNT variants, when oligodendroglial-like cell patterns prevail, or ganglion cells were difficult to discriminate from pre-existing neurons. Suggesting new terminology or major histopathological criteria did not satisfactorily increase the yield of histopathology agreement in four consecutive trials. To this end, the Task Force applied the WHO 2016 strategy of integrating phenotype analysis with molecular-genetic data obtained from panel sequencing and 450k methylation arrays. This strategy was helpful to distinguish DNT from GG variants in all cases. The Task Force recommends, therefore, to further develop diagnostic panels for the integration of phenotype-genotype analysis in order to reliably classify the spectrum of LEAT, carefully characterize clinically meaningful entities and make better use of published literature.