The following key terms were searched in the title, abstract or keywords of the published papers: “glioma or astrocytoma or glioblastoma” and “classification”, “treatment”, “incidence”, “gender or sex”, “contraceptive pills or hormone replacement therapy”, “pregnancy”, “aromatase expression or activity”, “estrogen or estradiol or estrogen receptor”, “androgen or testosterone or dihydrotestosterone or androgen receptor”, “progesterone or progesterone receptor”, “cortisol or corticosterol or glucocorticoid receptor”. This evidence concerns the gene CYP19A1 and central nervous system cancer.