<b><i>Introduction:</i></b> There is some evidence suggesting a link between <i>BRCA1/2</i> germline mutations and increased risk of gastric cancer. <b><i>Methods:</i></b> Endoscopic screening for stomach malignancies was performed in 120 <i>BRCA1</i> mutation carriers in order to evaluate the probability of detecting the tumor disease. <b><i>Results:</i></b> No instances of gastric cancer were revealed at the first visit. The analysis of atrophic changes performed by OLGA (Operative Link for Gastritis Assessment) criteria revealed that OLGA stages I–IV alterations were observed in 26 of 41 (63%) subjects aged &#x3e;50 years as compared to 29 of 79 (37%) in younger subjects (<i>p</i> = 0.007, χ² test). One <i>BRCA1</i> mutation carrier developed gastric cancer 4 years after the first visit for endoscopic examination. We performed next-generation sequencing analysis for this tumor and additional 4 archival gastric cancers obtained from <i>BRCA1/2</i> mutation carriers. Somatic loss of the remaining <i>BRCA1/2</i> allele was observed in 3 out of 5 tumors analyzed; all of these carcinomas, but none of the malignancies with the retained <i>BRCA1/2</i> copy, showed chromosomal instability. <b><i>Conclusion:</i></b> Taken together, these data justify further studies on the relationships between the <i>BRCA1/2</i> and gastric cancer.

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Aim. To increase the efficacy of systemic breast cancer therapy and reduce inappropriate prescriptions using individual immunohistochemical tumor characteristics, as well as to develop prognostic scales to ensure a tailored approach to adjuvant systemic treatment in breast cancer patients.   Materials and methods. We conducted a comprehensive study that included collection of literature data on clinical, pathomorphological, prognostic, and predictive factors of breast cancer, as well as a retrospective cohort study using the data from the cancer registry. We also performed histological and immunohistochemical examination of tumor tissue samples from breast cancer patients (for the retrospective cohort study) and statistical data analysis. A total of 1,216 patients with T1–2N0M0 breast cancer were included in this study. Histological and immunohistochemical examinations of tissue samples (paraffin blocks) were conducted in the laboratory of N. N. Petrov National Medical Research Center of Oncology. We stained slides for both routinely used markers (including estrogen receptors, progesterone receptors, HER2, and Ki-67) and other markers (CK14, FOXA1, FOXP3, PD-L1, P53, SMA, androgen receptors, E-cadherin, CD4, CD8, CK5 / 6, EGFR).We analyzed risk factors for lethal outcomes in patients from this group to develop prognostic scales and compared their results.   Results. We evaluated the most clinically and statistically significant factors affecting mortality. Using logistic regression, we chose 10 factors that had the greatest impact on the outcomes and then produced several scales, includinga 10-point regression scale (based on 10 most significant factors identified). Survival analysis in high-risk and low-risk patients using the regression scale demonstrated significant differences between these groups (р <0.00001). The assessment of adjuvant chemotherapy efficacy in the combined group of intermediate- and high-risk patients (as estimated by the regression model) showed that intermediate- and high-risk patients receiving adjuvant chemotherapy had significant differences in their survival (р = 0.0057). The regression scale for 10-year prognosis demonstrated sufficient sensitivity (58.05 %), specificity (69.47 %) and ef fectiveness (63.76 %).   Conclusion. Our regression prognostic scale includes markers with a high prognostic value. The multifactorial approach used in the developed regression scale for breast cancer 10-year prognosis increases its accuracy and reliability.