Endometrial stromal sarcoma: A review of rare mesenchymal uterine neoplasm V.A. Capozzi, L. Monfardini, V. Ceni, A. Cianciolo, D. Butera, M. Gaiano and R. Berretta Department of Gynecology and obstetrics of Parma, University of Parma, Parma, Italy Abstract Objective: This review aims to analyze the pathological aspects, diagnosis and treatment of rare mesenchy- mal uterine tumors. Methods: On August 2019, a systematic review of the literature was done on Pubmed, MEDLINE, Scopus, and Google Scholar search engines. The systematic review was carried out in agreement with the Preferred Reporting Items for Systematic Reviews and Meta-Analyzes statement (PRISMA). The following words and key phrases have been searched: “endometrial stromal sarcoma”, “low-grade endometrial stromal sarcoma”, “high-grade endometrial stromal sarcoma”, “uterine sarcoma”, “mesenchymal uterine tumors” and “uterine stromal sarcoma”. Across these platforms and research studies, five main aspects were analyzed: the biologi- cal characteristics of the neoplasms, the number of cases, the different therapeutic approaches used, the follow-up and the oncological outcomes. Results: Of the 94 studies initially identified, 55 were chosen selecting articles focusing on endometrial stro- mal sarcoma. Of these fifty-five studies, 46 were retrospective in design, 7 were reviews and 2 randomized phases III trials. Conclusion: Endometrial stromal sarcomas are rare mesenchymal uterine neoplasms and surgery represents the standard treatment. For uterus-limited disease, the remove en bloc with an intact resection of the tumor (without the use of morcellation) is strongly recommended. For advanced-stage disease, the standard surgi- cal treatment is adequate cytoreduction with metastatectomy. Pelvic and para-aortic lymphadenectomy is not recommended in patients with Low-grade Endometrial Stromal Sarcoma (ESS), while is not clear whether cytoreduction of advanced tumors improves patient survival in High-grade ESS. Administration of adjuvant radiotherapy or chemotherapy is not routinely used and its role is still debated. Key words: endometrial cancer, endometrial stromal sarcoma, high-grade, low-grade, mesenchymal uterine tumor. Introduction Endometrial stromal sarcoma (ESS) is part of a rare and complex group of mesenchymal uterine neo- plasms and represents 1% of all uterine malignancies. 1 ESS is the second most common mesenchymal uterine tumor after leiomyosarcomas and Figures 15% of malignant mesenchymal neoplasms of the uterus. 2 Nolan and Taylor first described the pathological fea- tures of these cancers and studied their clinical behav- ior in 1966. 3 The neoplasms were divided morphologically into two groups: one with pushing margins (stromal nodules) and one with infiltrating margins (endolymphatic stromal myosis or stromal sarcoma). Stroma nodule was considered benign while tumors with infiltrating margins were separated Received: April 19 2020. Accepted: July 30 2020. Correspondence: L. Monfardini, MD, Department of gynecology and obstetrics of Parma, University of Parma, via Gramsci 14, 43125, Parma, Italy. Email: luciano.monfardini@gmail.com 1 © 2020 Japan Society of Obstetrics and Gynecology doi:10.1111/jog.14436 J. Obstet. Gynaecol. Res. 2020