Objectives Objective of the study is to share the experience of a rare disease, Low-grade Endometrial Stromal Sarcoma, with few reports in the literature and the lack of standardization in therapy, especially in the preservation of fertility in young patients.

Methods Description of a case report for diagnosis and cytoreductive surgery to the definition of the exception conduct discussed in interprofessional meeting, literature survey and opinion of centers with greater expertise in oncology.

Results Tomography and ultrasound evidenced of complex cystic mass with multiple trabeculations and calcifications involving the entire abdomen, massive cystic multissepted, with thick septa and peritoneal nodules, which presented contrast enhancement, diffusely lining the peritoneal cavity, from the subdiaphragmatic surfaces to the pelvis. Tumoral marker (CA 125) presented alteration (3,630 U/ml). Pathological and immunohistochemistry exam showed malignant neoplasm of epithelial origin, Low-Grade Endometrial Stromal Sarcoma (ESS-LG). The patient was submitted in January 2018 to a cytoreductive surgery with preservation of the fertility, performed appendectomy, left salpingo-oophorectomy with resection of multiples peritoneal implants. Patient is currently in clinical follow-up, using megestrol acetate since March 2018, with no pregnancy schedule so far.

Conclusions ESS-LG are rare malignancies, it affects women in perimenopause and young people. The standard treatment is total hysterectomy and bilateral salpingo-oophorectomy, but in young patients consider the possibility of fertility-sparing to desire for gestation. The viability and safety are still limited due to few studies. Patients who chose to maintain fertility, had low recurrence rates and most of them presented a successful pregnancy, naturally, cesarean delivery, without complications.