PIK3CA and breast cancer: Highly penetrant breast cancer susceptibility genes 1 and 2 (BRCA1 and BRCA2) are found in a wide variety of organisms [38], also being the most common germline mutated genes, while the phosphatidylinositol-3-kinase (PIK3CA) is the second most common somatic mutated gene in BC patients, just after TP53 [30].