The frequency of somatic BRCA1 and BRCA2 PV may be between 1 and 3% of patients in unselected breast cancer populations [19,22,39,40,41,42,43,44], including ER+/HER2- breast cancer patients [19,40,42] and even higher in patients with ER+/HER2- mBC [12,21,45]. Here, ERBB2 is linked to breast cancer.