They have been reported to function during early mammary placode formation in the developing embryo (that is, Msx2, Tbx3, Wnt3a, and Fgfr1) or they are involved in breast cancer cell migration, invasion, and proliferation (that is, Barx2, Pdgfrb, Bmp6, and Jak3) [27]-[36]. The gene discussed is MSX2; the disease is breast cancer.