HER2, a transmembrane protein with tyrosine kinase activity, is overexpressed in many tumor types, especially breast cancer, where expression is linked to poor prognosis, resistance to chemotherapy, hormone therapy, and radiotherapy, and an elevated risk of metastasis and recurrence (Bookman et al., 2003; Liu et al., 2015; Zhou et al., 2015; Connell and Doherty, 2017; Yang et al., 2021). The gene discussed is ERBB2; the disease is breast cancer.