ERBB2 and breast cancer: TP53 and PIK3CA are the most common and could be related to cancer progression as well as affecting response to treatment.PI3K-inhibitors could play a role in treating HER2-positive BC, but warrants further investigations.The PIK3K/AKT pathway could be synergistic to the MAPK pathway, therefore MEK/ERK-inhibitors may prove to be useful in combination therapies.