The mean relative quantification (RQ) ± SD mRNA level of analyzed genes in the tissue material of BC was, respectively, PIP (57.37 ± 98.92), PIAS3 (3.07 ± 1.6), SOCS3 (1.25 ± 0.87), STAT5A (2.14 ± 1.86), and STAT5B (0.8 ± 0.54). This evidence concerns the gene STAT5B and breast cancer.