10236-NI-11 IMAGING FEATURES AND CONSIDERATION OF PROGRESSION PATTERN OF DIFFUSE HEMISPHERIC GLIOMA, H3 G34-MUTANT

Abstract BACKGROUND Diffuse hemispheric gliomas, H3 G34-mutant (DHG-G34m) are newly recognized pediatric-type diffuse high-grade gliomas. We describe detail imaging features of seven cases of DHG-G34m and consider about progression pattern of DHG-G34m. RESULTS H3 G34R/V was detected by sanger sequencing in all tumors. Mean age of onset was 16.5 years (range: 10-26). Tumors were located on frontal (n=2), parietal (n=2), temporal lobe (n=1) and insular cortex (n=1), respectively. In one case, gliomatosis cerebri-like multiple lesions involving the cortex and basal ganglia occurred. Magnetic resonance imaging showed T2/FLAIR high lesions with poor contrast enhancement in all cases. All tumors harbored restriction of diffusion. Strong accumulation of methionine was observed in six cases. Tumors of these cases harbored T2/FLAIR high lesions in the deep white matter which showed methionine accumulation. All patients underwent surgery (total resection in one case, partial resection in five cases, and biopsy in one case) followed by radiation chemotherapy. The mean progression free survival was 9.9 months (range: 1.6-33.1 months). All recurrent tumors harbored diffuse infiltration along the white matter adjacent to surgical cavity, which was temporarily reduced by bevacizumab, but eventually invaded into cerebral peduncle via pyramidal tract and into contralateral brain via corpus callosum or anterior commissure in six cases. Extensive infiltration of tumor cells into the contralateral brain and brain stem was confirmed in the autopsy brain of one case. The mean overall survival was 21.6 months (range: 8.9-48.3 months). CONCLUSION DHG-G34m showed deep white matter infiltration from the time of initial onset, which made gross total resection difficult. Residual lesions extensively infiltrated along the white matter and eventually invaded the brainstem and contralateral brain, leading to death.