ESR2 and neoplasm: The idea to activate ERβ as an endocrine strategy to treat TNBC primarily emerged from various studies showing that activation of this receptor by E2 or specific agonists such as ERB-041, WAY200070, or FERb 033 was able to notably reduce TNBC cell growth, arrest cell cycle at the G1 phase, block cell colony formation, inhibit TNBC cell invasiveness, and reduce tumor size in mice xenografts [41,43,44,84], as well as from other studies demonstrating ERβ to exert antitumoral actions.