RESUMEN
BACKGROUND: Endometrioid Stromal Sarcomas are an infrequent group of mesenchymal tumors that we must take into account in the differential diagnosis despite representing only 0.2% of tumors of the female genital tract, as they can go unnoticed until advanced stages. CASE PRESENTATION: Fifty-fourth year-old woman referred from the Urology department due to incidental finding of adnexal mass in MRI during examination after renoureteral colic, in the case of a 50 mm solid cystic mass in LE. MT were within the normal range, and the CT scan observed this mass in contact with the left ureter. The surgery was completed with hysterectomy and contralateral adnexectomy without incident and chemotherapy treatment was not added. The pathological result was ovarian tissue with low-grade endometrial sarcoma. Currently, after two years of follow-up, the patient remains stable without any recurrence of disease. CONCLUSIONS: Endometrioid stromal sarcomas are rare tumors that originate in the endometrial stroma, the ovarian location being rare. Management lies in surgical treatment, and adjuvant therapy is sometimes necessary in advanced stages.