DNET, MVNT, and now MGNT: A Newly Recognized Tumor Type in WHO CNS 5!

A subset of glioneuronal tumors that histologically resembled dysembryoplastic neuroepithelial tumors and rosette-forming glioneuronal tumors were found to have a recurrent dinucleotide variant in the PDGFRA gene, which encodes platelet-derived growth factor receptor α. On the basis of the morphology, molecular features, and common location of the septum pellucidum, these tumors were designated myxoid glioneuronal tumors and incorporated into the 5th edition of World Health Organization (WHO) Classification of CNS tumors (CNS WHO 2021). At our institution, there have been 4 cases in which the characteristic PDGFRA mutation has been identified. The clinical presentations, neuroimaging findings, differential diagnoses, pathology, and short-term outcomes will be discussed and compared with the recent literature. Patients were all young adults with a mean age of 29.75 years. Headache was the most common presenting symptom and correlated with obstructive hydrocephalus. All 4 cases were located along the septum pellucidum. One case was multifocal with an additional mass in the cerebral aqueduct. MR signal characteristics were similar to those of CSF on T1- and T2-weighted imaging. FLAIR showed more unique features of partial suppression except for a rim of bright signal. All patients had an indolent clinical course without recurrence or progression following resection. Myxoid glioneuronal tumors are rare, slow-growing tumors distinguished by their unique PDGFRA variants. The cases included in this study demonstrate the characteristic location and imaging appearances of the tumor type. Familiarity with these tumors and their imaging characteristics is critical to an accurate diagnosis, which may influence treatment.Learning Objective: To improve understanding and enhance the diagnostic accuracy of the recently described myxoid glioneuronal tumors.