Endometrial cancer has a worldwide mortality rate of approximately 20% and is the most common female reproductive system cancer. 1 Recently, the incidence rate of endometrial cancer has been steadily increasing each year. 2 The routine operation for endometrial cancer staging is hysterectomy and bilateral salpingo-oophorectomy, concomitant with pelvic and/or para-aortic lymphadenectomy. 3 Oophorectomy is performed even in young patients with low-risk, early-stage, estrogen-dependent endometrial cancer, which occasionally reveals coexisting malignant tumors. 4 A cohort study found that the 5-and 10-year cumulative incidence of women with endometrial cancer who subsequently developed ovarian cancer was 1.0% and 1.3%, respectively, which was low. 5 The survival of premenopausal women with a decreased risk of endometrial cancer after preserving their ovaries that are not