Indeed, metastatic BC to the stomach is rare, and the majority of these patients have ER-positive disease, but ER expression is not only present in BC, but in other (gynecological) tumors as well, such as uterine tumors, ovarian, endometrial, and gastric cancer [4,21,22,23,24,25,26,27,28]. Here, ESR1 is linked to breast cancer.