ERBB2 and breast cancer: Among them, some variants that are considered of “uncertain significance” in familial breast cancer studies testing BRCA1 and BRCA2. Other germline variants were located in ESR1, ERBB2, PIK3CA, KMT2C and ZNF217, genes considered of great importance in the development and outcome of breast cancer [1,8,31,37,38,39,40,41].