A Diffuse Leptomeningeal Glioneuronal Tumor Without Diffuse Leptomeningeal Involvement: Detailed Molecular and Clinical Characterization.

Prior to their provisional WHO classification as a distinct entity in 2016, diffuse leptomeningeal glioneuronal tumors (DLGNT) were often regarded as diffuse leptomeningeal presentations of oligodendrogliomas or extraventricular neurocytomas. Their classification as a distinct entity partly relies on their pattern of growth, but DLGNTs without radiological leptomeningeal involvement have been described. In a patient with a DLGNT of the spinal cord without evidence of leptomeningeal involvement, we review in depth the clinical course and the histologic and molecular features of the neoplasm, in the context of other reported cases without diffuse leptomeningeal involvement. Our findings highlight the advantages of molecular analysis in making accurate diagnoses on small spinal tissue samples and underline the need for more long-term clinical follow-up of these rare neoplasms to inform treatment decisions.