Primary diffuse leptomeningeal gliomatosis: do we miss the diagnosis?

Abstract Primary diffuse leptomeningeal gliomatosis (PDLG) is characterized by diffuse infiltration of the leptomeningeal space by neoplastic glial cells without evidence of intra-parenchymatous primary tumor. We report a case of PDLG in a 68-year-old man, who died 1 month after onset of symptoms. The diagnosis was made on autopsy data. We discuss the particularities of this entity, which is not registered in the WHO classification of tumors of the central nervous system (2016). In case of an unexplained inflammatory meningeal process and in the presence of atypical cells in the cerebrospinal fluid, PDLG needs to be considered. This diagnosis of PDLG has to be confirmed by meningeal imaging-guided biopsy, which must be repeated if necessary. .