KISS1 and breast cancer: In breast cancer, Kiss-1/GPR54 system, estrogen-related gene expression profiles, regulation, and transcript isoforms of KiSS1 gene have been described [20–24] and Xie et al. showed significant relationship between lymph node involvement and absence of Kiss-1 expression in early breast carcinoma patients (P = 0.001) [25]; however, there is no information about whether the presence of a polymorphism could be involved in the differential KiSS1 gene expression.