This prospective observational study aimed to evaluate the prognostic impact of receptor conversion in breast cancer patients treated with NCT.Of the 423 consecutive patients who had residual disease in the breast after NCT, 55 (13.0%) changed from HR (+) to HR (−), 23 (5.4%) changed from HR (−) to HR (+), 27 (6.4%) changed from HER2 (+) to HER2 (−), and 13 (3.1%) changed from HER2 (−) to HER2 (+). This evidence concerns the gene ERBB2 and breast cancer.