Diffuse leptomeningeal glioneuronal tumor (DLGNT)

DLGNT is a rare CNS tumor that has been characterized radiographically by leptomeningeal enhancement on MRI that may involve the posterior fossa, brain stem region, and spinal cord.[69] Intraparenchymal lesions, when present, typically involve the spinal cord.[69] Localized intramedullary glioneuronal tumors without leptomeningeal dissemination and with histomorphological, immunophenotypic, and genomic characteristics similar to DLGNT have been reported.[70]

DLGNT showed a distinctive epigenetic profile on DNA methylation arrays, and unsupervised clustering of array data applied to 30 cases defined two subclasses of DLGNT: methylation class (MC)-1 (n = 17) and MC-2 (n = 13).[69] Of note, many of the array-defined cases had originally been diagnosed as other entities (e.g., primitive neuroectodermal tumors, pilocytic astrocytoma, and anaplastic astrocytoma). Patients with DLGNT-MC-1 were diagnosed at an earlier age than were patients with DLGNT-MC-2 (5 years vs. 14 years, respectively). The 5-year OS rate was higher for patients with DLGNT-MC-1 than for those with DLGNT-MC-2 (100% vs. 43%, respectively). Genomic findings from the 30 cases of methylation array–defined DLGNT are provided below: