PIK3CA and breast cancer: Pre‐clinical evidence also showed that PTEN‐null tumors, including breast cancers, are sensitive to the inhibition of PI3K pathway and in particular to the targeting of specific nodes of the signaling route, such as the β isoform of PI3K (Jia et al, 2008; Wee et al, 2008; Hancox et al, 2015) and AKT (Chen et al, 2006; Vasudevan et al, 2009; Sangai et al, 2012).