In contrast to ER-negative breast cancer, where the GA + AA genotype of rs2046210 was shown to be associated with a downregulation of the levels of ESR1 expression [22] in adjacent normal tissue, we found that significantly higher levels of ESR1 expression in eutopic endometrial tissue of younger women with endometriosis are associated with the GA + AA genotype of the SNV. This evidence concerns the gene ESR1 and endometriosis.