The PIK3CA gene, which encodes phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha, is mutated in a number of tumors, including glioblastomas, gastric cancers, lung cancers, ovarian cancers, hepatocellular carcinomas, endometrial carcinomas, brain cancers, and breast cancers [7].The higher frequency of PIK3CA missense mutations in luminal breast cancer samples prompted us to ask how PIK3CA mutations interact with other mutated genes to trigger cancer progression and metastases. This evidence concerns the gene PIK3CA and breast cancer.