A pathologic complete response (pCR) to NAT, marked by the absence of residual cancer burden (RCB-0) in the breast and regional lymph nodes, is a strong predictor of favorable long-term outcomes, especially in HER2-positive and triple-negative (TN) breast cancer subtypes; however, its prognostic value is less robust in hormone receptor (HR)-positive/HER2-negative disease3. This evidence concerns the gene ERBB2 and breast cancer.