CDK4 and breast carcinoma: In the era of new drugs, such as CDK4/6 inhibitors, with proven efficacy in metastatic settings in combination with fulvestrant or aromatase inhibitors, their role in neoadjuvant settings has been widely investigated, and early clinical data on the neoadjuvant treatment of hormone receptor-positive/HER2-negative breast cancer is promising [35,36,37,38].