FOXO1 and endometriosis: Endometriosis was also more common in the left ovary, which is consistent with previous studies.[21] The prevalence of endometriosis in the left ovary is explained by the presence of the sigmoid colon, which delays the spread of retrograde menstrual blood, resulting in weak and slowed fluid flow in the left hemipelvis.[21] Accordingly, OECs originate from the epithelium of endometriotic tissue and are associated with FOXO1 expression loss, similar to UECs.