Although sarcomatous transformations of IDH-wildtype glioblastoma into gliosarcomas, and oligodendrogliomas into oligosarcomas, have been well described for decades [9, 13, 14], the diagnosis of IDH-mutant astrocytoma with sarcomatous differentiation has only rarely been published [7, 15]. Here, IDH1 is linked to astrocytoma (excluding glioblastoma).