Patients with five breast cancer subtypes were included in the study: luminal A (<i>n</i> = 130), luminal B (<i>n</i> = 196, including HER2-, <i>n</i> = 100; HER2+, <i>n</i> = 96), HER2+ (<i>n</i> = 36), and TNBC (<i>n</i> = 43); they underwent surgery, during which tumor tissue was removed along with a margin of healthy tissue (control material). The gene discussed is ERBB2; the disease is breast cancer.