Hormone receptor-positive (HR+) cancers (luminal A and luminal B/HER2-) respond favorably to ChT in percentages below 15%, with the utility of ChT in this patient category still under debate, while TNBC represents an aggressive subtype of breast cancer with reserved prognosis and a high mortality rate but with promising results regarding response to PST. The gene discussed is ERBB2; the disease is cancer.