In 2001, Sørlie et al. further classified luminal-like breast cancer into luminal A and luminal B subtypes and demonstrated that different subtypes of breast cancer were statistically associated with prognosis [3]: the luminal A subtype was associated with the best prognosis, followed by the luminal B subtype, whereas the Her-2-positive and basal-like subtypes were associated with the worst prognosis. This evidence concerns the gene ERBB2 and breast cancer.