Background: STUMP ecompass a group of uterine mesenchymal neoplasms in which the clinical behavior cannot be predicted on morphological grounds. A malignant clinical evolution is seen in approximately 10-20% of cases. When STUMP relapse, the label of “low-grade leiomyosarcoma” is sometimes found to be appropriate, though current histopathological criteria for uterine leiomyosarcoma (so called “Stanford criteria”) would exclude even the existence of low-grade uterine smooth muscle neoplasms. As they express ER and PR, hormonal treatment with GnRH inhibitors or aromatase inhibitors (AIs) may represent a therapeutic option. Methods: From October 2015, we have been treating with hormonal therapy relapsing patients with an initial diagnosis of STUMP, whose pathological aspect on retrospect was consistent with a “low-grade uterine leiomyosarcoma”. We identified 8 patients. Pathological diagnosis was centrally reviewed by expert sarcoma pathologists. Results: Eight pts were treated: 7 in first line; 1 pt in 4th line, following failure of chemotherapy (gemcitabine and taxotere, adriamycin and dacarbazine, trabectedin). Two premenopauseal pts were treated with GnRH inhibitors, 2 with a combination of GnRh inhibitors and an aromatase inhibitor, 3 with aromatase inhibitors only and 1 with selective progesterone-receptor modulator. 7 patients are evaluable for response and all of them had a partial response as best response. Median progression-free survival was 31 months. Conclusions: In our series, all patients with a centrally reviewed diagnosis retrospectively consistent with a “low grade uterine leiomyosarcoma” responded to hormonal treatment. Therefore, these pts may make up a subgroup with therapeutic and prognostic relevance. “Stanford criteria” need to be re-assessed, in an effort to improve prognostic and therapeutic stratification of uterine smooth muscle neoplasms, possibly shrinking the scope of currently defined STUMP.