The overexpression of human epidermal growth factor receptor 2 (HER2), a transmembrane glycoprotein epidermal growth factor receptor (EGFR) with tyrosine kinase activity, is observed in 15%–20% of newly diagnosed breast cancer (BC) patients and is historically associated with a more aggressive phenotype, increased risk of recurrence, and poorer outcome [1, 2]. The gene discussed is ERBB2; the disease is breast cancer.