Introduction/Background Uterine sarcomas are quite rare and their frequency is only 3–7% of uterine tumors. According to available data, PD-L1 receptor is expressed in approximately 47% of uterine mesenchymal neoplasms, and ER hormone receptors are expressed in 63% of uterine sarcomas. Although there is almost no data on these issues.

We considered it appropriate to investigate immunohistochemical expression of PD-L1, ER and PR in mesenchymal tumors of different types and degrees of malignancy.

Methodology The study group included 51 cases of primary mesenchymal tumors of the uterus of patients aged 35 to 75. Receptor expression was studied immunohistochemically, of which 28/51 (55%) patients had leiomyosarcoma, 8/51 (16%) had STUMP, and 15/51 (29%) had endometrial stromal sarcoma.

Results In leiomyosarcomas PD-L1 expression was detected in 17/28 (61%) cases, varying from 20 to 90%, with a statistically significant positive correlation with the degree of malignancy of leiomyosarcomas (r=.79, p<0.0001). Negative correlation with immunohistochemical expression of estrogen and progesterone receptors (ER, PR) was detected (r=-.52, p<0.0001/r=-.64, p<0.0001). None of the ER and PR positive tumors showed expression of PD-L1.

ER expression was significantly lower in leiomyosarcomas of intermediate and high-grade malignancy compared to leiomyosarcomas of low-grade malignancy (p= 0.001). ER expression was also statistically significantly decreased in high-grade endometrial stromal sarcomas compared to low-grade endometrial stromal sarcomas (p=0.003). A statistically significant negative correlation of immunohistochemical expression of PR with the degree of malignancy of lesions was established, both in leiomyosarcomas (p<0.0001) and in endometrial stromal sarcomas (p<0.002).

Conclusion Based on the results of the study, in the case of high-grade malignant leiomyosarcomas, it is recommended to evaluate the immunohistochemical expression of PD-L1 in order to prescribe potential immunotherapy, and in low-grade malignant stromal tumors, it is recommended to evaluate the immunohistochemical expression of ER and PR in order to prescribe hormone therapy.

Disclosures No disclosures, no conflict of interest.