Diffuse leptomeningeal glioneuronal tumor in a child masquerading as an
intramedullary spinal pilocytic astrocytoma
Diffuse leptomeningeal glioneuronal tumor (DLGNT) is characterized by
widespread leptomeningeal lesions with focal parenchymal involvement. We
present a child with a large intramedullary spinal cord lesion, whose
biopsy revealed a biphasic astrocytic tumor consistent with pilocytic
astrocytoma. Next-generation sequencing revealed a KIAA1549-BRAF
fusion, 1p/19q co-deletion, and no IDH1 mutation. Methylation
profiling demonstrated a calibrated class score of 0.98 for DLGNT.
Despite morphologic similarities to pilocytic astrocytoma and lack of
oligodendroglial/neuronal components or leptomeningeal dissemination,
the molecular profile definitively classified the tumor as DLGNT. This
case highlights the importance of molecular and genetic testing in
diagnosing pediatric central nervous system tumors.