Jiao and colleagues examined a cohort of grades II to IV diffuse gliomas for IDH, ATRX, TP53, CIC and FUBP1 mutations as well as 1p/19q codeletion and classified the tumors into ‘I-CF’ (IDH1/2 mutation with either 1p/19q loss, CIC mutation or FUBP1 mutation), ‘I-A’ (IDH1/2 mutation and ATRX mutation) and ‘I-X’ gliomas (neither I-CF nor I-A). The gene discussed is ATRX; the disease is glioma.