Given that in-vivo mouse-model gene expression profiles strongly associated a subset of mesenchymal tumors with hypoxia-response gene expression, which suggests a linkage between mesenchymal tumors and hypoxia (so called ‘mesenchymal-like hypoxia-dependent’ or ‘MES2’ tumors) [17, 18], we questioned whether embolization may have had any causative role in the higher-grade mesenchymal transformation of this IDH-mutant astrocytoma. The gene discussed is IDH1; the disease is astrocytoma (excluding glioblastoma).