In restricted analyses using t-distributed stochastic neighbor embedding (t-SNE)-analysis we confirmed the distinctiveness of the DNA methylation profile of the sarcomatous tumors which were clearly separated from their primary tumor manifestations and from conventional oligodendrogliomas, as well as from IDH-wildtype glioblastomas, from high- and low-grade supra- and infratentorial IDH-mutant astrocytomas, and from primary mismatch repair deficient IDH-mutant astrocytomas (PMMRDIA) (Fig. 1, Supplementary tables, online resource). The gene discussed is IDH2; the disease is neoplasm.