PATH-41. THE DEVELOPMENT OF PRIMITIVE NEURONAL COMPONENT AT FIRST PROGRESSION OF MALIGNANT GLIOMA, A CASE SERIES

Abstract

Abstract A subset of malignant gliomas are found to have solid-looking primitive nodules which confer a diagnosis of glioblastoma with primitive neuronal component (GBM-PNC). These tumors are associated with higher rates of isocitrate dehydrogenase (IDH) mutations and increased responsiveness to platinum-based therapies, however they are also associated with a high rate of cerebrospinal fluid (CSF) dissemination. We review four patients treated at our institution with a prior diagnosis of malignant glioma who were found to have GBM-PNC at resection of recurrent disease and evaluate the clinical significance of the development of a primitive neuronal component. Of the 4 patients, 3 had previously been diagnosed with glioblastoma with a disease-free interval after radiation and temozolomide of 17.8 years, 2.4 years, and 1.6 years. The 4th patient was diagnosed 2 years prior with a WHO grade 2 IDH mutant astrocytoma and had only been treated surgically prior to disease progression. At recurrence, all patients developed cystic masses adjacent to prior surgical site in frontal lobe and/or temporal lobe. While no patients had spinal cord symptoms, as a result of the primitive component found at re-resection 3 out of 4 patients underwent spinal cord imaging. Two patients were found to have cauda equina enhancement favored to represent CSF dissemination. This is in line with the 40% CSF dissemination reported in other case series of diagnosis of GBM-PNC and far greater than 1.1% reported for glioblastoma. In this case series, the of development of primitive neuronal component at malignant glioma recurrence was associated with radiographic appearance of a cystic mass with significant vasogenic edema as well as high rates of CSF dissemination. The clinical implication of platinum responsiveness will also be presented.