Introduction/Background Uterine smooth muscle tumor of uncertain malignant potential (STUMP) represents the ‘grey zone’ between leiomyomas(LM) and leiomyosarcomas (LMS). This rare neoplasm usually affects young women and very little is known about prognostic factors except the negative impact of morcellation. The aim of this systematic review of the literature was to identify whether there may be a hormonal impact in terms of recurrence, evaluating the histological and/or immunohistochemical characteristics reported

Methodology Articles published in English were retrieved from electronic databases from the inception to October 2023 according to PRISMA guidelines. Studies assessing histological features at immunohistochemistry (IHC) such as Estrogen receptors (ERr), Progesteron receptors (PRr), p53, p16 and/or ki67 were included for the final analysis.

Results 40 articles were included. Among 584 patients collected, 108 cases (18,5%) recurred, in agreement with literature data (74 as STUMP and 34 as LMS). The mean time to recurrence was 43 months. Whether the IHC was reported, a significant association for recurrence was found with necrosis (p 0.014), mitosis/10 HPF (p 0.010), p53 (p 0.020), ki67 (p <0.0001), ERr (p 0.008), PRr (p <0.0001) and p16 (p 0.0001), but not for cellular atypia (p 0.78) and p16 (p 0.26). Particularly, we found that the negativity of Estrogen receptors (OR 2.97, 95% CI 1.30–6.76, p 0.001) and Progesteron receptors (OR 7.69, 95% CI 2.90–20.37, p <0.0001) were associated with higher risk of recurrence.

Conclusion The absence of ERr/PRr is associated with higher risk of relapse. From these data we deduce that a possible hormonal stimulus could not negatively impact the prognosis, allowing us to perform less invasive surgeries in case of STUMP e.g. preserving the ovaries with a certain safety in young patients, or to evaluate the possibility of hormone replacement therapy in patients who are submitted to radical surgery.

Disclosures The authors declare no conflict of interest.