ESR2 and breast cancer: Out of these 16 genes, there were 14 genes—AREG, CLDN, CYP19A1, DKK1, EGFR, ESR2, FOS, IGF1, KRAS, NCOA1, NCOR1, NR2F6, PGR, RARB, and STC2—common among 17β-estradiol, breast cancer, and endometriosis (Table 2, Table 6 and Table 7).