SURG-02. ANAPLASTIC PLEOMORPHIC XANTHOASTROCYTOMA WITH LEPTOMENINGEAL DISSEMINATION PRESENTING WITH CRANIAL NEUROPATHY IN AN ADULT PATIENT: ILLUSTRATIVE CASE AND REVIEW OF THE LITERATURE

Abstract INTRODUCTION Anaplastic pleomorphic xanthoastrocytomas (APXA) are very rare, grade III malignant astrocytic glial neoplasms first described as a distinct entity in the 2016 World Health Organization (WHO) Classification of Tumors of the Central Nervous System (CNS). They are generally seen in pediatric and young adult patients as supratentorial lesions with both solid and cystic components and have a high propensity for recurrence despite local treatment. APXAs occasionally demonstrate leptomeningeal dissemination (LMD) but extremely seldom at the time of diagnosis. They are typically treated via surgical resection with adjuvant chemoradiation, although there is no standard of care for adjuvant therapy. Case Presentation: The authors describe the case of a 37-year-old male with a history of seizures since age 11 who presented with four months of worsening headache, increasingly frequent seizures, and diplopia with right cranial nerve III palsy. Imaging at the time of diagnosis of his seizure disorder as a child demonstrated a small left temporal lesion, which remained stable on imaging for over 20 years and was never biopsied, however MRI at current presentation showed significant interval enlargement with intralesional hemorrhage and leptomeningeal enhancement involving the left temporal and parietal lobes, left internal auditory canal, and right oculomotor nerve. He underwent surgical resection with gross total resection achieved and pathology revealed WHO Grade III pleomorphic xanthoastrocytoma with ATG7::RAF1 fusion, 9p21 deletion, and TERT promoter mutation on next generation sequencing. This was followed by adjuvant whole brain radiation with boost and treatment with MEK inhibitor cobimetinib. His postoperative course was remarkable for intermittent speech difficulty and improving right third nerve palsy. CONCLUSION We describe the unusual presentation of an already exceedingly rare primary CNS tumor, namely APXA in an adult patient with LMD and cranial neuropathy at the time of diagnosis, and detail tailored adjuvant therapy based on genomic profiling.