P14.82 Glioneuronal tumors - a rare tumor entity with diagnostic and therapeutic challenges: report of two cases and review of literature

Abstract

Abstract BACKGROUND The 2007 WHO classification of brain tumors first encompassed two new entities of glioneuronal tumors, including papillary glioneuronal tumors (PGNT) and rosette-forming glioneuronal tumours. The reviewed version of the 2016 WHO classification additionally included diffuse leptomeningeal glioneuronal tumours. The histopathological, genetic, and clinical understanding of glioneuronal tumors is currently evolving, however there are no guidelines for diagnostic and clinical management yet. MATERIAL AND METHODS We report two male patients with glioneuronal tumors and performed a review of literature. RESULTS The first patient was diagnosed with a PGNT (MIB-1 proliferation index = 5%) located in the right parietal lobe at the age of 33 years and received surgical resection. Two years later, the tumor recurred in the same location. A second tumor resection was performed followed by concomitant radiochemotherapy with temozolomide (60/2 Gray). A next-generation sequencing gene panel (Oncomine) confirmed the initial diagnosis of a PGNT. The patient has remained in remission for the past 10 years. The second patient developed complex partial seizures which were first misdiagnosed as anxiety disorder at the age of 26 years. An MRI scan revealed a contrast-enhancing bifrontal cystic lesions 5 years later and he received a gross total tumor resection. The diagnosis of a glioneuronal tumor was made, however molecular pathology and methylation analysis were not able to classify the tumor entity further. There was no evidence of tumor recurrence one year after surgery and he remained seizure-free with antiepileptic treatment. CONCLUSION Glioneuronal tumors encompass rare and heterogenous tumor entities which primarily present in young patients and often show a favorable clinical course. Although the increasing number of reports in the literature have improved our understanding of these tumors, uncertainty remains in diagnostic challenging cases and patients with progressive disease after surgery. The value of next-generation sequencing and the choice of adjuvant treatment modalities have not been systematically evaluated in this patient group.