The expression levels of β2-M protein demonstrate significant differences in the four breast cancer molecular subtypes (P = 0.034); the rate of positive staining was 56.25% (Luminal A), 53.33% (Luminal B), 84.61% (Overexpression of HER-2) and 73.68% (Basal-like). This evidence concerns the gene ERBB2 and breast cancer.