ERBB2 and breast cancer: Triple‐negative breast cancer (TNBC), the most aggressive BC subtype, comprises 15%–20% of cases [3, 4, 5, 6] and is defined by the lack of estrogen receptor (ER), progesterone receptor (PR), and HER‐2 expression [3, 4, 5, 6, 7, 8, 9, 10].