Finally, using immunohistochemical data from the TCGA, we were able to separate the breast cancer patients into one of four molecular subtypes—luminal A (ER positive and/or PR positive and HER2 negative), luminal B (ER positive and/or PR positive and HER2 positive), triple negative/basal-like (ER negative, PR negative, and HER2 negative), and HER2 type (ER negative, PR negative, and HER2 positive). This evidence concerns the gene ERBB2 and breast cancer.