RARE-48. CHARACTERISTICS AND OUTCOME OF DIFFUSE LEPTOMENINGEAL GLIONEURONAL TUMOR (DLGNT): A SINGLE INSTITUTION EXPERIENCE

Diffuse leptomeningeal glioneuronal tumors (DLGNT) are rare with an unknown etiology and unestablished incidence. Most frequently reported genetic alteration is KIAA1549-BRAF fusion. We present four DLGNT cases diagnosed between 2005–2018. Patient 1 is a female who presented with a 2-year history of back pain subsequently diagnosed with pilocytic astrocytoma. Re-imaging 3 months post-resection revealed a low grade glioneuronal tumor with BRAF duplication. Patient 2 is a female who presented with recurrent vomiting, dizziness, and hydrocephalus. The patient underwent biopsy which was consistent with oligodendrogliomatosis; no genetic analysis was done. Patient 3 is a male who presented with worsening headaches and intermittent vomiting. Approximately 5 months after resection, imaging showed leptomeningeal disease and further testing revealed KIAA1549-BRAF fusion and 1p deletion. Patient 4 is a male who presented with hydrocephalus. Imaging showed disseminated leptomeningeal enhancement without a dominant mass lesion; biopsy and clinical history confirmed the diagnosis. All four patients received chemotherapy, Patients 1 and 3 underwent radiation therapy, and Patient 3 received a MEK-inhibitor to which he had a great response. However, the patient was non-compliant and had PD which continued despite re-starting therapy. Patients 1, 2, and 3 have died of progressive disease; survival was Patient 1, 276 days, Patient 2, approximately 7 years and 8 months, and Patient 3, 2 years and 11 months. Patient 4 remains alive with disease 4.5 years from diagnosis. There is much to be learned about this rare, poorly understood disease but hope for improvement through therapeutic targeting of the MAPK pathway.