High-grade glioneuronal tumor with an ARHGEF2-NTRK1 fusion gene.

Here, we report a highly unusual case of high-grade glioneuronal tumor with a neurotrophic tropomyosin receptor kinase (NTRK) fusion gene. A 13-year-old girl presented with headache and vomiting and MRI detected two cystic lesions bilaterally in the frontal areas with surrounding edema. The left larger tumor was removed by left frontal craniotomy. The tumor was diagnosed as a high-grade glioneuronal tumor, unclassified. Methylation profiling classified it as a diffuse leptomeningeal glioneuronal tumor (DLGNT) with low confidence. This tumor showed genotypes frequently found in DLGNT such as 1p/19q codeletion without IDH mutation and, however, did not have the typical DLGNT clinical and histological features. RNA sequencing identified an ARHGEF2 (encoding Rho/Rac guanine nucleotide exchange factor 2)-NTRK1 fusion gene. The presence of recurrent NTRK fusion in glioneuronal tumors has an important implication in the clinical decision making and opens up a possibility of novel targeted therapy.