PIK3CA and breast cancer: Dysregulation of the PI3K/AKT pathway in BC is commonly caused by RTK activation, such as in the case of HER2 amplification, KRAS mutations, and PI3K alterations such as PIK3CA-activating mutations, and less often, PIK3CB, PIK3R1, PIK3R2 mutations, AKT1-activating mutations, inactivation of tumor suppressor genes such as PTEN, and TSC1/2 [10].