Among agents that interfere with PI3K/AKT/mTOR signaling, inhibitors of mTOR are furthest in clinical development and have demonstrated efficacy in renal cell carcinomas as well as in patients with neuroendocrine tumors of pancreatic origin and in postmenopausal patients with hormone receptor positive breast cancer [13], [14], [15], [16]. This evidence concerns the gene MTOR and breast cancer.