The finding that normal PMCs express ER-α and respond to tamoxifen suggests that tamoxifen may be beneficial in other peritoneal malignancies, such as mCRC, gastric cancer, pancreatic cancer and malignant mesothelioma, where PMC derived stromal interactions and ER-α/ER-β expression ratios are also important [68,103,104,105,164]. Here, ESR1 is linked to gastric cancer.