Seven studies investigated ER protein expression in adenomyosis lesions compared to the eutopic endometrium, without differentiation of the isoform (Tamaya et al., 1979; Konopka et al., 1998; Zhang et al., 1999; Ueki et al., 2004; Zhang et al., 2008; Khan et al., 2016; Zeng et al., 2017). This evidence concerns the gene ESR1 and adenomyosis.