ERBB2 and breast carcinoma: With the introduction of cyclin‐dependent kinase 4/6 (CDK4/6) inhibitors, the treatment of metastatic hormone‐receptor (HR)‐positive, human epidermal growth factor 2 (HER2)‐negative (HR+HER2−) breast cancer has made substantial progress and the combination of endocrine therapy with CDK4/6 inhibitors now prevails in the management of advanced HR‐positive breast cancer [1].