Alice Métais

Recent studies have reported very rare, low-grade, diffusely infiltrative tumours (LGDIT), SMARCB1-mutant, expanding the spectrum of central nervous system (CNS) SMARCB1-deficient tumours [1-3]. Despite their indolent clinical behaviour compared with aggressive atypical teratoid and rhabdoid tumours (ATRTs), malignant transformation of LGDIT into ATRT has been described and both share a similar DNA-methylation profile, particularly close to the ATRT-MYC subgroup [1, 4].

1 Introduction Extraventricular neurocytoma (EVN) is a rare neuroepithelial tumour that historically has been defined histologically by its resemblance to central neurocytoma while arising outside the ventricular system. In the pre-molecular era, this anatomical distinction, together with shared morphologic features such as uniform round cells, a neuropil-like background, and synaptophysin expression, formed the basis of its classification.