T‐DM1 and Trastuzumab are approved for HER2‐positive breast cancers that express either 2+ or 3+ staining on IHC, whereas T‐DXd is approved for HER2 breast cancers that express 1+, 2+, or 3+ HER2 expression on IHC. The gene discussed is ERBB2; the disease is breast carcinoma.