EP14.01 A RARE CNS PRIMARY COLLISION TUMOR IDH-WILDTYPE GLIOBLASTOMA WITH COEXISTENT EPENDYMOMA A CASE REPORT

Abstract BACKGROUND Gliomas arise from glial progenitor cells and constitute a heterogeneous group of tumors. They include mainly glioblastomas, astrocytomas, oligodendrogliomas and ependymomas. IDH-wildtype Glioblastoma are the most common primary CNS malignant tumors. Ependymomas arise from the lining cells of the ventricular system, and less common in the brain parenchyma. A collision tumor is a neoplastic lesion comprised of two or more distinct cell populations. MATERIAL AND METHODS A case report of 54-year-old woman harboring IDH-wildtype glioblastoma with concomitant grade 3 ependymoma with 19q deletion. RESULTS A 54-year-old woman presented with a 2-week history of headache and progressive left hemiparesis. Brain MRI showed an intra-axial lesion in the right frontal lobe with contrast enhancement and calcifications in SWI. She underwent craniotomy with gross total resection (EOR 95%). Histopathological examination identified two distinct tumor components: one with features of a high-grade glioma: extensive necrosis and microvascular proliferation, positive immunoreactivity for GFAP and S100 protein. The other component exhibited ependymal differentiation characterized by perivascular pseudorosettes, morphologically corresponding to ependymoma. Immunohistochemistry, PCR and FISH analysis, revealed that the high-grade glioma component was IDH-wildtype and lacked 1p/19q codeletion, consistent with the diagnosis of IDH-wildtype Glioblastoma WHO grade 4. The ependymoma component was WHO grade 3 with 19q deletion only. ZFTA fusion and YAP1 fusion were not performed. No co-deletion was found in any component The pathologically calculated proportion in the sample was 60% ependymoma and 40% glioblastoma. Neuroaxis MRI and CSF analysis showed no evidence of distal tumor activity. Stupp protocol was given to treat the most aggressive component. Currently she has 1 year progression-free survival, with complete response by RANO criteria; functionally KPS 100% and ECOG 0. CONCLUSION This is an extraordinarily rare case of a CNS collision tumor that represents a challenge in diagnosis and management. These tumors are scantily described with only two cases reported.