Adult diffuse leptomeningeal glioneuronal tumour with limited leptomeningeal involvement, lack of 1p deletion and BRAF V600E mutation.

Diffuse leptomeningeal glioneuronal tumours (DLGNT) are rare primary CNS tumours, traditionally characterised by leptomeningeal growth and usually affecting children. A recent large study defined DLGNT on a molecular basis, of which all demonstrated 1p deletions. The vast majority also demonstrated MAPK/ERK pathway activations, however BRAF V600E mutation has not been previously documented in adult cases. In this case report, we describe an unusual cerebral DLGNT, with limited leptomeningeal spread, intact 1p status and a BRAF V600E mutation.