Two important studies, the CREATE-X and KATHERINE trials, emphasize the importance of detecting any residual invasive disease in patients with TN and HER2+ breast cancer, respectively, showing that OS can be improved with the administration of additional adjuvant chemotherapy.18,19 Therefore, the aim of the present pathology substudy was to quantify the residual disease post-NST and the residual disease missed with biopsies for the different subtypes of breast cancer. The gene discussed is ERBB2; the disease is breast cancer.