These results revealed that breast cancers display a wide range of tumor heterogeneity caused by alterations in multiple factors, including somatically mutated driver genes (e.g., TP53, PIK3CA, AKT1, CBFB, GATA3, and MAP3K1), gene amplifications (ERBB2), and hormonally regulated gene programs (driven primarily by estrogen, progesterone, and androgen steroids) [2, 3, 6]. This evidence concerns the gene ERBB2 and breast cancer.