Serous endometrial intraepithelial carcinoma (SEIC) and clear cell carcinoma of the endometrium (CCEC) belong to pathogenetic type II without evidence of hyperestrogenism, are often detected late in the course of the disease, and are characterized by an aggressive course. Currently, there is increasing interest in the role of local content and metabolism of steroid hormones in organs and tissues in various pathologies, including the development of malignant tumors. Purpose of the study. To determine the local level of sex hormones in patients with SEIC and CCEC. Patients and methods. The study included 21 patients with SEIC and 20 patients with CCEC. The control group consisted of 20 patients who had undergone surgical treatment for uterine myoma. All patients were treated at the National Medical Research Center for Oncology, Rostov‑on‑ Don, the Russian Federation Ministry of Health. The local levels of estrogens and androgens were determined in the tumor tissue, the perifocal zone, endometrial tissue unaffected by the tumor process, and the fallopian tube tissue in patients with SEIC and CCEC. In the control group, the local level of sex hormones was determined in intact 10 % homogenic endometrial tissue. Results. The data were analyzed, and the results demonstrated that the tumors and peritumoral tissues exhibited a depletion of estradiol (E2), a saturation of testosterone, and an extreme saturation of estriol (E3). The consequence of this imbalance was the predominance of fetal placental estrogen (E3), which was detected not only in the tumor tissue but also in distant parts of the endometrium and uterine tubes. In these regions, the concentration of E3 exceeded that of intact endometrium by a factor of more than five. A comparison of estrogen receptor (ER) levels revealed elevated levels in samples of the tumor, its perifocal zone, distant endometrium, and fallopian tubes. This finding indicated a predominance of ERα over ERβ. Conclusion. The local hormonal background of rare forms of non‑endometrioid endometrial carcinomas exhibits distinctive characteristics, including the replacement of the influence of classical estrogen (E2) by fetal, placental E3. Additionally, there is a notable prevalence of the REα type over REβ, along with hyperandrogenization of tissues, which culminates in the formation of a unique low‑differentiated tumor with pronounced biological aggressiveness.
