Glioneuronal Tumour With Neurocytic Differentiation (GNTN): a Molecularly Defined Tumour Type Formerly Referred to as Extraventricular Neurocytoma.

We report 14 previously unpublished tumours with a robust extraventricular neurocytoma DNA methylation profile, independent of original histopathologic diagnosis or anatomic location.

In addition, a single case exhibited an NTRK2 fusion.

Histologically, tumours exhibited neurocytic differentiation with neuropil islands and a minor glial component, while immunohistochemistry showed frequent OLIG2 expression, contrasting with the typical immunophenotype of central neurocytoma.

Clinical follow-up (median 33.2 months) showed predominantly lower grade behaviour, with occasional recurrence.