NR4A1 and breast cancer: 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.