ERBB2 and breast carcinoma: With the application of HER‐2 fluorescent in situ hybridization and HER‐2 immunohistochemistry which are standard clinical tests for HER‐2 gene amplification 35, 36, HER‐2 gene amplification or protein overexpression has been extensively studied in breast cancer 37, 38, 39, 40, much less is known about genetic variants and mutations that might have an impact on the risk or therapy of breast cancer.