We found no differences between groups with regard to self-evaluation of cognitive functioning problems; the mean rating was 3.60, SD = 2.81, in patients with IDH1-mut tumours vs. 3.67, SD = 2.95 in patients with IDH1-wt (U = 579.000, z = 0.18, p = 0.857); 40 (53%) patients with IDH1-wt tumour gave a self-assessment of 0–3 vs. 8 (53%) patients with IDH1-mut, score 4–6 was given by 18 (24%) vs. 5 (33%) patients and a score above 7 17 (23%) vs. 2 patients (13%). The gene discussed is IDH1; the disease is neoplasm.