HER2-low tumors have an IHC score of 1 or 2 for HER2 expression, but no evidence of HER2 amplification on molecular ISH test (ISH = negative),13,14 while patients with HER2-ultralow BC show ≤10% of cancer cells with faint or incomplete membrane staining and IHC score of 0.15 Another important approach for targeted therapeutic strategy in BC is determined by hormone receptor status. The gene discussed is ERBB2; the disease is breast cancer.