Generally, it has been shown that tissue expression of RANK and RANKL is increased in healthy breast tissue compared with breast cancer tissue [39, 40], that tissue expression of RANKL varies with changing levels of sex hormones during the menstrual cycle [7, 41, 42], and that it is higher in premenopausal than in postmenopausal women [43, 44]. This evidence concerns the gene TNFRSF11A and breast cancer.