Low-grade endometrial stromal sarcoma arising from extrauterine deep infiltrating endometriosis: a rare, but important differential diagnosis and short review of the literature

• Low-grade endometrial stromal sarcoma (LG-ESS) is a rare uterine malignancy; extrauterine LG-ESS arising from endometriosis is exceptionally uncommon (<80 reported cases). • Diagnosis is challenging, as imaging lacks specific features; confirmation relies on histopathology and immunohistochemistry (ER, PR, CD10, WT1). • Case report: A 32-year-old woman with LG-ESS arising from deep infiltrating endometriosis was treated with maximal cytoreductive surgery and adjuvant aromatase inhibitor therapy. • Fertility-sparing surgery can be discussed but is genereally not recommended in extrauterine LG-ESS; complete surgical resection with adjuvant endocrine therapy is the preferred approach. • Clinical relevance: Early recognition and correct diagnosis, standardized treatment strategies, and long-term follow-up are essential to improve outcomes in this rare malignancy. Low-grade endometrial stroma sarcoma is a very rare mesenchymal neoplasm, that is usually found inside the uterine corpus. It is very uncommon that LG-ESS arises from extrauterine foci. We report the case of a 31-year-old patient diagnosed with extrauterine LG-ESS arising from deep infiltrating endometriosis. Primary symptoms, diagnostic workflow, operating method, and the outcome will be described, as well as a short review of the current literature about the optimal treatment for young LG-ESS patients within the reproductive window. Long-term surveillance is imperative for patients with LG-ESS given the potential for late recurrences. Although extrauterine LG-ESS represents an exceedingly rare gynecologic malignancy, establishing standardized treatment approaches is critical to optimize therapeutic efficacy and improve patient outcomes.