Similarly, a 14-gene immunoglobulin B-cell signature (IGG) has been identified as a key variable associated with a better prognosis and a higher probability of pCR in HER2-positive (HER2+) breast cancer treated with anti-HER2-based chemotherapy.25, 26, 27, 28 The IGG signature in combination with tumor burden (i.e., tumor size and nodal status), and two other gene signatures tracking proliferation and luminal features, have been integrated into a single assay, called HER2DX, and validated retrospectively across >7 studies and >1800 patients. Here, ERBB2 is linked to breast cancer.