The PTEN/Akt/mTOR pathway has been described: 1) as one of the major pathways in the regulation of mammary stem/progenitor cells, 2) to confer resistance to conventional therapy, and 3) to play a central role in the viability and maintenance of cancer stem cells in breast, promoting proliferation and the inhibition of apoptosis [17,46]. Here, PTEN is linked to cancer.