INNV-13. INDOLENT H3 K27-ALTERED DIFFUSE MIDLINE GLIOMA

Abstract

Abstract INTRODUCTION H3 K27-altered diffuse midline glioma (DMG) is an aggressive central nervous system tumor that is universally fatal with a median survival of 8-12 months after diagnosis. Here we present a patient who was incidentally found to have a lesion within the right thalamus on brain magnetic resonance imaging (MRI). Twelve years later, she was found to have a brain mass within the same area with pathology consistent with an H3 K27-altered DMG. Case Description: A 14-year-old female presented with new onset left sided numbness and weakness, blurry vision and a right sided temporal headache. Her past medical history is significant for severe persistent asthma and anoxic brain injury secondary to a cardiopulmonary arrest at 2-years-of-age due to an asthma exacerbation. She has had multiple MRIs of her brain since her initial insult which initially showed the presence of a T2/FLAIR hyperintense lesion within the right medial thalamus in addition to chronic central nervous system changes. The right thalamic lesion was stable in size between images obtained at 2-years and 4-years of age. Her current physical exam is significant for decreased strength to her left upper and lower extremities. Brain MRI with and without contrast is obtained, demonstrating partial effacement of the third ventricle due to mass effect from an enlarging mass from the right thalamus. Biopsy of the lesion demonstrated an H3 K27-altered DMG, WHO grade 4. Our patient went on to receive palliative radiation therapy with 59.4 Gy over 33 fractions. DISCUSSION This case illustrates an unusual presentation of an H3 K27-altered DMG with an indolent course, diagnosed twelve years after the initial MRI finding. This proposes the possibility of multiple factors playing a role in the oncogenesis of these aggressive tumors and that further research is warranted.