There are many such observed issues in breast cancer, for example, the co-existence of mutations of PIK3CA and amplification of ERBB2 have been linked with resistance to HER2-targeting drugs lapatinib and trastuzumab (Fontanella et al., 2014), which provides the rationale of combining HER2 and PI3K inhibitors in different clinical trials. This evidence concerns the gene ERBB2 and breast carcinoma.