ESR2 and breast cancer: Tamoxifen, a selective ERα modulator that has been reported to activate nuclear ERα in SMCs,[83] was linked to a high frequency of adenomyosis in breast cancer patients,[84, 85] and was used to generate adenomyosis mouse models.[86] Besides, ERα was linked to the loss of noradrenergic nerve fibers in adenomyosis.[87] In the realm of adenomyosis pathogenesis, the estrogen receptor beta (ERβ), encoded by the ESR2 gene, has been a focus of greater scrutiny compared to ERα.