The hypothesis of the ongoing European Breast Cancer Research Association of Surgical Trialists (EUBREAST)-01 (GBG104, NCT04101851) trial is to prove the oncological safety of omission of axillary SLNB after pathologic complete response (pCR) in the breast in response to NAST for TNBC and HER2-positive disease in initially clinical node-negative (cN0) patients. This evidence concerns the gene ERBB2 and breast cancer.