As a result, using flow cytometry, it was revealed that only in the culture of OPC-like cells obtained from the astrocytomas, IDH-mut, grade 3 and grade 4, and from oligodendroglioma, IDH-mut, grade 3, but not in the culture of similar neoplasms having grade 2, the appearance of MES-like cells is observed (Figure 4a). The gene discussed is IDH2; the disease is oligodendroglioma.