Patent Blue SLN in Early Ovarian Cancer Prospective Study (FIGO I-II) Evaluating Patent Blue SLN Mapping. Injection Into IP/UO Ligaments in Situ. Goals: Assess Feasibility and Accuracy vs Standard Lymphadenectomy to Minimize Surgical Morbidity

Patients, with an early-stage ovarian cancer ESOC (FIGO stage I \& II), will be recruited. In our setting, the preoperative staging is based on : * MRI finding (O-RADs classification 4 OR 5) * Thoraco-abdominal CT scan * Gastrointestinal endoscopy (if needed) * Ovarian tumor biomarkers (CA 125, CA 19-9, Alpha-FP, HE4...) Or patients referred to our department for management of an ESOC with after an adnexectomy for ovarian mass. These patients will receive a complete surgery for ovarian cancer : Peritoneal cytology, Bilateral adnexectomy, hysterectomy, pelvic lymphadenectomy, paraaortic lymphadenectomy, omentectomy and peritoneal biopsies. Prior to the adnexectomy, surgeon will inject in subperitoneal space of the infundibular ligament (1 ml of patent blue dye: 0.5 ml in ventral and 0.5 ml in dorsal) and of the utero-ovarian ligament (1 ml of patent blue dye: 0.5 ml in ventral and 0.5 ml in dorsal). Then we will wait for 15 minutes: during which we will proceed to the adnexectomy. After 15 min, the retroperitoneal space of the pelvic and para-aortic regions was opened, and the presence of Sentinelle lymph Nodes (SLNs) was examined visually. The surgeon will record the number and location of the resected SLNs. Following the identification and removal of the SLNs, a complete systematic bilateral pelvic and para-aortic lymphadenectomy is performed. All specimen will be subject to histology analysis. The collected data: 1. PreOperative informations: * Sociodemographic data : Age, Body Mass Index, Menopausal status.. * History: Family history of cancer, Comorbidity, surgical history.. * Ovarian tumor biomarkers * PreOperative imaging: MRI, CT scan, Ultrasonography * Presumed FIGO stage (I or II) 2. Peri-operative data: * SLN procedure: injection timing, Injected volume and site, Time to visual detection, site and number of detection * Operative complications: vessel injury, nerve injury and allergic reaction to dye 3. Pathological finding: * tumor characterization: type (serous, mucinous,...), grade and tumor size * SLN analysis: SLN frozen section, SLN final ultrastaging * Non-SLN status after complete lymphadenectomy * Final FIGO stage 4. Post-operative follow-up * Hospital stay duration * Post-operative complications (within Clavien-Dindo classification) * Adjuvant therapy