One out of three (1/3) available CSF-cytology results from patients with an IDH-mutant glioma was reported as “atypical cells present”, 2/5 CSF-cytology results from patients with metastatic breast cancer were reported as “suspicious” or “consistent” with metastatic carcinoma and 1/7 CSF-cytology results from patients with metastatic lung cancer were reported as “atypical cells present”. This evidence concerns the gene IDH2 and central nervous system cancer.