PLAG‐Family Amplified CNS Embryonal Tumour With PLAG1 Immunohistochemical Expression: Expanding the Spectrum of Diagnostic Tools

PLAG(L)-altered tumours have recently emerged as a novel category of Central Nervous System (CNS) tumours, although they are not yet included in the most recent WHO Classification. In 2022, genome-wide DNA-methylation analysis of cases previously diagnosed as CNS embryonal tumours, high-grade gliomas, or unclassifiable neoplasms led to the identification of the ‘CNS embryonal tumour with PLAG-family amplification’ methylation class, characterised by PLAGL1 or PLAGL2 amplification [1]. In 2023, two embryonal tumours harbouring PLAG1 fusions, which share clinical, radiological, histopathological, immunohistochemical and epigenetic features with CNS embryonal tumours with PLAG-family amplification, were also reported [2]. Here, we describe a case of CNS embryonal tumour with PLAGL2 amplification, contributing new evidence to the characterisation of this evolving entity. To the best of our knowledge, we also present the first report of PLAG1 immunostaining positivity, suggesting its potential as a useful diagnostic tool in routine practice.