Introduction: Oligodendroglioma is a low grade glioma (LGG) comprising approximately 5% of gliomas. The paradigm that primary central nervous system (CNS) tumors, specifically these LGG are restricted to local advancement rather than metastatic spread of disease has been challenged by several reports demonstrating both disseminated CNS and even distant corporal metastases by primary anaplastic oliogodendrogliomas. Over the past decade, molecular and genetic characterization of tumor specimens has become a commonplace, nearly defining, feature of newly diagnosed LGG. The 1p/19q, Isocitrate Dehydrogenase 1 (IDH1) mutation, and methylation of the O6-methylguanine-methyltransferase (MGMT) promoter are genetic changes associated with improved progression-free survival.

Methods: Our case is the first report of leptomeningeal spread and distant CNS metastasis of oligodendroglioma despite favorable genetic subtyping, including IDH1 mutation, 1p/19q codeletion, and MGMT promoter methylation. This unique case prompted a review of the literature, which identified several salient features about our case, which are also assicated with risk factors for LGG progression, including initial tumor size and subtotal resection. Futhermore, we retrospectively performed genetic analysis of our tumor specimens for genetic mutations not yet commonly used in clinical practice in the hopes of facilitating the accumulation of data to identify which patients may be at risk for this aggressive, rare, and late sequelae of a commonly described low grade lesion.

Results: Our tumor specimen, including the metastatic lesion, continued to demonstrate favorable mutations at IDH1, 1p/19q (codeletion), and MGMT promoter. Results of investigational genetic analysis is forthcoming.

Conclusions: Both genetic and surgical factors impact likelihood of metastatic spread of low grade glioma. As more patients survive late into their disease course thanks to adjuvant treatment, previously rare sequelae may become more common. Thus, identification of genetic markers which portend a more malignant course and warrant more aggressive initial resection will be increasingly valuable.

Patient Care: Identification of genetic mutations which portend increased likelihood for leptomeningeal or metastatic spread would guide practitioners at the time of initial resection. Patients may be willing to withstand some degree of neurologic deficit if their tumor would be more likely to disseminate.

Learning Objectives: 1) Describe the clinically actionable genetic mutations relevant to oligodendroglioma 2) Describe the factors in surgical resection which are associated with likelihood of CNS dissemination. 3) Describe the investigational genetic mutations which may be associated with CNS dissemination.

References: Berger, M. S., Deliganis, A. V., Dobbins, J., & Keles, G. E. (1994). The effect of extent of resection on recurrence in patients with low grade cerebral hemisphere gliomas. Cancer, 74(6), 1784–1791. http://doi.org/10.1002/1097-0142(19940915)74:6<1784::AID-CNCR2820740622>3.0.CO;2-D Cahill, D. P., Louis, D. N., & Cairncross, J. G. (2015). Molecular background of oligodendroglioma: 1p/19q, IDH, TERT, CIC and FUBP1. CNS Oncology, 4(5), 287–294. http://doi.org/10.2217/cns.15.32