Background: High incidence and mortality of breast cancer (BC) require a constant search for the most informative and effective methods of diagnosis and treatment evaluation. The purpose of the study was to analyze phenotypic characteristics of cancer stem cells in tumor tissues and regional metastases of breast cancer (BC). Methods: The study included 20 BC patients with regional metastases (lymph nodes) aged 32-74 years, mean age 56.1±3.3 years. IHC analysis was performed on sections from paraffin blocks of tumors using monoclonal mouse antibodies to CD44 (156-3C11 Thermo Scientific) at a dilution of 1:2500 and polyclonal rabbit antibodies to CD133 (Cloud-Clone Corp.) at a dilution of 1:700 using the Thermo Scientific automated stainer. Membrane staining and staining intensity were evaluated: 0, 1+ weak, 2+ moderate, 3+ strong staining. CD44 expression was considered positive when staining was detected in more than 10% (cut-off) tumor cells. CD133 expression was considered positive when staining was detected in more than 5% (cut-off) of the tumor. Results: CD44 + expression was detected in 80% of breast tumor tissues (16 samples), while in 20% this marker was not determined. The average CD44 expression was 27.2±13.9%. The expression of CD44 in regional metastases (RM) from BC was 35% (from 0 to 30%), on average 17.0±6.8%. When distributed according to the χ2 criterion in the tumor and RM, an association between factorial and resultant signs was statistically significant (8.286, at p < 0.004). CD133+ expression in tumor tissues was detected in 80%, with an average expression level of 56.0±14.6%, with a predominance of positive cytoplasmic staining in 60%. Determination of this marker in BC RM gave a positive result in 15% (3 samples), with expression fluctuations from 0 to 60%, the average level was 33.0±15.4%. When distributed according to the χ2 criterion in the tumor and RM, an association between factorial and resultant signs was statistically significant (16.942, at p < 0.001). Conclusions: Determination of tumor cells with the stem phenotype directly in the tissue of primary BC tumors and in tissues of regional metastases demonstrated that the percentage of CD44+ and CD133+ cells in the primary BC tumor was higher.