The problem of finding reliable clinical and morphological criteria for diagnosis and prognosis of serous borderline ovarian tumors, their relationship with the risk of developing of low-grade serous ovarian carcinomas (LGSC) in future is still relevant. This study is devoted to research and highlight of precursors that allow dividing women with serous borderline ovarian tumors (SBOT) into risk group for occurrence of LGSC within next 5 years. The study included 22 patients with FIGO stage I-II SBOT aged 24 to 46 years, 9 (39.13%) of whom were diagnosed with high-grade serous ovarian carcinoma next 5 years. Two study groups were formed: the control group (n = 13), which included patients with SBOT without further development of LGSC, and the main group (n = 9), which included women with emerging LGSCs. We studied expression of immunohistochemical markers Ki-67, MMP-9, p53, Bcl-2, E-cadherin, and also a diameter and localization of the tumor. As a result of the study, it was found that patients with diameter of the SBOT≥10 cm (χ² = 6.0, p <0.03), FIGO stage II (χ² = 4.7, p <0.03) and Ki-67 expression ≥10% (χ² = 9.03, p <0.03) have a high risk of developing LGSC within next 5 years. In the group of women who underwent LGSC development, there was a tendency to more pronounced expression of MMP-9 (χ² = 4.18, p <0.04) and moderate and pronounced expression of Bcl-2 (χ² = 9.66, p = 0.008). According to our data, markers Ki-67, MMP-9, Bcl-2 are prognostic and can be used as markers of LGSC risk in women with a history of SBOT. Tumor diameter ≥10 cm is also a predictor.