RT Journal Article SR Electronic T1 PAX6 is frequently expressed in ependymal tumours and associated with prognostic relevant subgroups JF Journal of Clinical Pathology JO J Clin Pathol FD BMJ Publishing Group Ltd and Association of Clinical Pathologists SP jclinpath-2021-207526 DO 10.1136/jclinpath-2021-207526 A1 Julian Tabasaran A1 Martin Schuhmann A1 Martin Ebinger A1 Jürgen Honegger A1 Mirjam Renovanz A1 Jens Schittenhelm YR 2021 UL http://jcp.bmj.com/content/early/2021/08/24/jclinpath-2021-207526.abstract AB Aims An ependymoma shows divergent morphological and molecular features depending on their location. The paired box 6 (PAX6) transcription factor is a putative tumour suppressor and drives cancer cells towards a stem cell-like state. A transcriptome study reported high PAX6 expression in ependymal tumours, but data on protein expression are lacking.Methods We, therefore, analysed PAX6 expression by immunohistochemistry in 172 ependymoma samples and correlated its expression to histology, WHO grade, anatomical location and molecular subgroups.Results Mean PAX6 nuclear expression in ependymoma was 27.5% (95% CI 23.3 to 31.7). PAX6 expression in subependymoma (mean: 5%) was significantly lower compared with myxopapillary (30%), WHO grade II (26%) and anaplastic ependymoma (35%). Supratentorial ependymomas also displayed significant lower PAX6 levels (15%) compared with spinal cord tumours (30%). Expression levels in YAP1-fused ependymoma (41%) were higher compared with REL-associated protein (RELA)-fusion positive tumours (17%), while PAX6 expression was similar in posterior fossa group A (33%) and B (29%) ependymomas. Kaplan-Meier analysis in RELA-fusion positive ependymomas and posterior fossa group B showed a significant better outcome for PAX6 at or above the cut-off of 19.45% compared with tumours with PAX6 below the cut-off.Conclusions We demonstrate that PAX6 is frequently expressed in human ependymal tumours and immunohistochemistry may be helpful in determining prognostic relevant subgroups.Data are available on reasonable request. All data relevant to the study are included in the article or uploaded as online supplemental information. The individual datasets generated during and/or analysed during the current study are not publicly available due to privacy of research participants but are available from the corresponding author on reasonable request.