Type 2 diabetes mellitus (T2DM) and breast cancer are diagnosed in the same individual more frequently than would be expected. The metabolic alterations that occur in T2DM can probably explain this link. However, to date, the studies done have not been sufficient to identify the mechanisms underlying the link between T2DM and breast cancer. It is therefore critical to identify new molecular targets that link T2DM and breast cancer and to develop new therapeutic approaches that prevent and control breast cancer initiation, promotion and progression in patients with T2DM.