In one of the oligodendroglioma cases with two tumor recurrences (SU-156), the classifier predicted the primary CNS WHO grade 2 tumor as an oligodendroglioma, IDH-mutant and 1p/19q-codeleted subclass (calibrated score 0.65787), and the paired CNS WHO grade 3 recurrences were assigned to the novel oligosarcoma, IDH-mutant subclass (calibrated scores > 0.90, Fig. 2). The gene discussed is IDH1; the disease is neoplasm.