Introduction/Background Endometrial stromal sarcoma (ESS) is a rare uterine tumor and the second most frequent type of uterine mesenchymal neoplasia after uterine leiomyosarcoma. The objective of this study is to determine the clinical features associated with different types of ESS.

Methodology Retrospective observational study of patients diagnosed with LMS in the Gregorio Marañon Hospital (1985 – 2021).

Results Table 1 shows results.Low-grade ESS are more frequent in premenopausal women (71,4%). They are usually diagnosed in early stages (85,7%). The most frequent clinical form of presentation is vaginal bleeding, a fact that we did not observe in our analysis, where incidentally diagnosis after a surgery for presumed benign uterine leiomyoma is the most frequent form of presentation. It is usually a tumor with an indolent course but tends to recur, even many years after diagnosis. However, in our analysis we did not find any recurrence, probably due to a small sample size.High-grade ESS are worse prognosis tumors. Usually diagnosis as advanced stages (54,6%), they tend to present as vaginal bleeding (65,2%). High recurrence rates (63,1%), usually as metastatic disease (75% of them), promote high mortality rate (72.7%).USS is a rare tumor typical of postmenopausal women (66,6%). It is a very aggressive tumor that carries a poor prognosis. Usually diagnosed in advanced stages but our sample does not corroborate (n=3, 3 early stages).Initial management requires surgical treatment as long as the tumor is resectable (85.3%). The systematic performance of pelvic and para-aortic lymphadenectomy is controversial since it has not been shown to increase survival

Conclusion ESS are rare, heterogeneous tumors and the available evidence on their management is poor. The subtype is known as an influent feature in prognosis. A higher disease-free survival was observed in low-grade SSE (85.7%) and a higher mortality in high-grade SSE (72.7%).