The Significance of Mutation in the Epithelioid Glioblastoma Subtype: A Systematic Literature Review and a Case Report with a Unique Intraventricular Topography.

Epithelioid glioblastoma (E-GBM) is an exceedingly rare subtype of isocitrate dehydrogenase (IDH)-wildtype glioblastoma, first included in the WHO 2016 classification and characterized by a dominant population of epithelioid cells. Its histological and molecular defining features remain troublesome. The significance of mutations to pathological diagnosis and surgical outcome has drawn increasing attention given their promising potential for future adjuvant therapies. Herein, we describe a unique case of an E-GBM in the atrium of the left lateral ventricle and comprehensively analyze the importance of status in a cohort of 211 E-GBMs from the literature. Our patient was a 40-year-old man with occipital pain. His brain MRI revealed a large intraventricular tumor at the same location as a signal change found 10 years earlier with no additional follow-up. He underwent gross total tumor removal followed by conventional adjuvant treatment. Histopathological diagnosis was consistent with IDH-wildtype E-GBM WHO grade 4 with pleomorphic xanthoastrocytoma-like areas. p.V600 mutation was demonstrated in the tumoral genetic study. In the cohort analyzed, male patients predominated (63%), the median age was 32 years old, and the 5-year survival rate following diagnosis was 4.2%. mutations were found in 60.3% of the tumors overall, with this rate increasing to 78.3% in young adults (19-49 years,  < .001). Presence of mutations associated with tumor progression ( = .001), the event usually leading to death ( < .001). In conclusion, our study supports the importance of genetic p.V600 mutation analysis because its presence not only points to an E-GBM diagnosis but may also promote tumor progression.