The immunoexpression levels in mastopathy vs. tumor of PIP (6.17 ± 3.52 vs. 3.44 ± 3.52, p < 0.001), PIAS3 (cytoplasmic) (8.94 ± 2.59 vs. 7.49 ± 3.81, p < 0.001), STAT5 (cytoplasmic) (8.77 ± 2.63 vs. 6.43 ± 4.43, p < 0.001), STAT5-P (3.6 ± 0.7 vs. 2.53 ± 1.24, p < 0.01), and PRLR (9.22 ± 2.7 vs. 5.99 ± 2.83, p < 0.001) (Figure 2A,B,D–F) were significantly lower in tumors (n = 554) than in mastopathy (n = 61). This evidence concerns the gene STAT5B and neoplasm.