Elaborating on the suggestions in the ISN-Haarlem guidelines, a recent study on adult diffuse low- and high-grade gliomas demonstrated that the integrated morphological and molecular diagnosis (incorporating information on ATRX, IDH and 1p/19q codeletion) had significantly greater prognostic power for overall and progression-free survival than the original, histopathological diagnosis. The gene discussed is IDH2; the disease is glioma.