BackgroundSynchronous endometrial disorders have been poorly studied in women with endometrioid borderline ovarian tumors (EBOT). The aims of this study were to investigate the risk of endometrial disorders among women with EBOT and associated factors, as well as their oncological and fertility outcomes.ResultsThis retrospective study included 33 women with EBOT. Their mean age was 41.9 years, and endometria were evaluated in 25 of these patients. The prevalence of synchronous endometrial disorders was 52.0% (n = 13/25) and this incidence was 41.4% (n = 46/111) after systematic analysis. Univariable analysis showed that EBOT patients who were younger, nulliparous, and had experienced abnormal vaginal bleeding were more likely to have synchronous endometrial disorders. The median follow-up was 54 months (range: 14-250 months), and three patients (10.3%) developed recurrences. No deaths due to EBOT were recorded. Among the nine nulliparous women treated conservatively who were attempting to conceive, only one (11.1%) pregnancy resulted in a live birth.ConclusionsSynchronous endometrial disorders are common in women with EBOT, especially in those who are younger, nulliparous, and have experienced abnormal vaginal bleeding. Thus, endometrial sampling should be performed in women with EBOT undergoing conservative surgery, and a hysterectomy should be performed in cases requiring radical treatment.