We identified clonogenic endometrial cells, SUSD2+ eMSC and N-cadherin+ eEPC concurrently in menstrual fluid and peritoneal fluid of women with and without endometriosis (31) and also clonogenic endometrial cells and SSEA-1+ eEPC in menstrual fluid of normal women (30, 31). Here, FUT4 is linked to endometriosis.