PATH-38. DISSEMINATED “MYXOID GLIONEURONAL TUMOR, PDGFRA P. K385-MUTANT” IN AN ADOLESCENT MANAGED WITH OBSERVATION AND WITHOUT ANY ADJUVANT THERAPY

Abstract

Abstract INTRODUCTION Myxoid glioneuronal tumor, PDGFRA p. K385-mutant (MGNT) is a recently described central nervous system tumor entity typically arising from the septum pellucidum and molecularly defined by mutation of the PDGFRA oncogene. The tumor is clinically benign, can be disseminated at presentation and is managed by surgical resection with or without adjuvant therapy (Chemotherapy / Radiation). CASE REPORT: 16yr old female presented to the children’s emergency with 6-week history of increasing intensity of acute on chronic frontal headaches and single episode of seizure like activity. She did not have nausea, vomiting or any cognitive or visual disturbances. Neurological exam was normal with no evidence of papilledema. Magnetic Resonance imaging (MRI) of the brain showed a large intraventricular mass arising from the right lateral ventricle and the septum pellucidum with dissemination into the periventricular white matter, suprasellar region, right thalamus, genu and splenium of the corpus callosum and multiple foci seen in the inferior aspect of the brain stem involving the pons and medulla. There was no evidence of obstructive hydrocephalus and the spine was normal. After an initial endoscopic biopsy failed molecular testing, she underwent an open biopsy which confirmed the diagnosis of MGNT histologically and NGS testing of the tumor revealed mutation at codon 385 (leucine replacing lysine) in the PDGFRA oncogene (k385l). Since the tumor was disseminated and the headache was controlled with symptomatic treatment, she was managed with regular follow up without surgery, adjuvant chemotherapy or radiation. The patient is doing well at 8 months follow up without any symptoms and stable lesions on the MRI. CONCLUSION Based on our experience and literature review, MGNT with PDGFRA-k385l mutation is a clinically benign tumor even though it can be disseminated at presentation and can be managed conservatively without any adjuvant therapy.