Introduction/Background Endometrioid Borderline Ovarian Tumor (EBOT) is a rare subtype of borderline ovarian malignancies. This study aimed to determine the prognosis of a series of EBOT.

Methodology A retrospective review of patients with EBOT treated in or referred to our institutions. A centralized histological review by a reference pathologist; data on the clinical characteristics, management (surgical and medical) and oncologic outcomes of patients were required for inclusion.

Forty-eight patients were identified Median age was 52 years (range 14–89). Fourteen patients underwent a conservative surgery and 32 a bilateral salpingo-oophorectomy (unknown in 2 cases). Two patients had bilateral tumors. Forty-three patients had stage-I disease and 5 patients had a stage-II disease (10%). Stromal microinvasion and intraepithelial carcinoma was observed in 6 (12%) and in 13 (27%) patients respectively. Endometriosis was histologically associated in 12 patients (25%). Synchronous endometrial disease was found in 7 (24%) of 29 patients with endometrial histological evaluation.The median follow-up was 72 months (range 6–146 months). Two patients developed a recurrence after cystectomy in form of borderline disease (5%). No death related to EBOT occurred.

Conclusion Peritoneal restaging surgery should be performed if not realized initially, since 5% of EBOTS are diagnosed at stage II-III. Fertility-sparing surgery seems a safe option in selected patients. Because synchronous endometrial diseases including endometrial carcinoma are frequent, systematic hysterectomy (or endometrial sampling in case of fertility-sparing surgery) is mandatory. Prognosis is generally excellent. Recurrence is a rare event (6%), but it can occur in the form of invasive disease.