Diffuse Leptomeningeal Glioneuronal Tumor with FGFR1 Mutation in a 29-Year-Old Male

This study reports on diffuse leptomeningeal glioneuronal tumor (DL-GNT) in a 29- year-old male. DLGNT is a rare central nervous system (CNS) tumor mostly seen in children and only few cases have been reported in adult patients. Our patient presented with a chronic headache that lasted for five months. MR imaging showed mild hydrocephalus, multiple rim-enhancing nodular lesions in the suprasellar cistern, diffuse leptomeningeal enhancement in the lumbosacral area, and multiple small non-enhancing cyst-appearing lesions not suppressed on fluid attenuated inversion recovery (FLAIR) images in the bilateral basal ganglia, thalami, and cerebral hemispheres. Under the impression of germ cell tumor with leptomeningeal seeding, the patient underwent trans-sphenoidal tumor removal. DL-GNT was pathologically confirmed and FGFR1 mutation was detected through a next-generation sequencing test. In conclusion, a combination of leptomeningeal enhancement and multiple parenchymal non-enhancing cyst-appearing lesions not suppressed on FLAIR images may be helpful for differential diagnosis despite overlapping imaging features with many other CNS diseases that have leptomeningeal enhancement