Low Grade Extrauterine Endometrial Stromal Sarcoma Arising from Peritoneum Endometriosis: A Case Report and Literature Review

Introduction: Endometrial stromal sarcoma (ESS) is an uncommon condition that accounts for approximately 0.2% of all reproductive tract malignancies. Among the various subtypes of ESS, low-grade extrauterine endometrial stromal sarcoma (LG-EESS) is even rarer and has only been reported in a limited number of case studies. Case Presentation: We reported a case of LG-EESS in a 35-year-old woman with a five-year history of stage IV endometriosis. The patient presented with chronic abdominopelvic pain and dysmenorrhea. Transvaginal ultrasound showed bilateral tubo-ovarian complexes with multicystic structures, while MRI revealed solid lesions with T1 iso signal, T2 hypersignal, and diffusion restriction, indicating metastatic implantation extending to the peritoneum and subhepatic region. A core needle biopsy confirmed LG-EESS, and immunohistochemistry showed CD10 positivity, aiding in the diagnosis and distinguishing it from other tumors. Conclusions: Our case highlights the potential utility of preoperative diagnostic imaging, particularly MRI, in the evaluation of LG-EESS. Additionally, it emphasizes the importance of considering the possibility of extrauterine ESS, as this tumor exhibits histopathological features and clinical behavior similar to its uterine counterpart.