Chromosome arm 1q gain is an adverse prognostic factor in localized and diffuse leptomeningeal glioneuronal tumors with BRAF gene fusion and 1p deletion

Excerpt

We previously described a series of localized intramedullary glioneuronal tumors limited to the spinal cord with histomorphologic, immunophenotypic, and molecular characteristics of diffuse leptomeningeal glioneuronal tumor (DLGNT), a newly added provisional entry in the current World Health Organization classification of central nervous system tumors [1, 3]. These localized spinal tumors and DLGNTs are characterized by the concomitant presence of KIAA1549‐BRAF fusion and chromosome arm 1p deletion [6]. Both have OLIG2-expressing oligodendrocyte-like tumor cells that are positive for synaptophysin and negative for GFAP [5]. Neuropil-like islands surrounded by neurocytic cells and variable amounts of ganglion cell differentiation are additional distinct features of both diseases [1]. However, despite this histomorphologic, immunophenotypic, and molecular resemblance, it remains uncertain whether the localized spinal BRAF-fused and 1p-deleted glioneuronal tumors are nosologically related to DLGNT, in which predominant and widespread leptomeningeal dissemination at presentation, often without a recognizable parenchymal component, is a defining feature [3]. …