Specifically, the loss of HER2 is defined as a negative HER2 status in a previously HER2-positive tumor (i.e., a change from a 3+ IHC score or 2+/ISH-amplified to an IHC 0-1+ or 2+/ISH-negative), implying that the residual tumor no longer has HER2 overexpression or amplification at surgery, after neoadjuvant treatment[11]. The gene discussed is ERBB2; the disease is neoplasm.