Moreover, in a cohort of 353 patients with BC treated with NAC (55.8% HR+, 15.6% HR+/HER2+, 9.6% HER2+, and 19% TN), the multivariate analysis with other clinicopathological factors, such as Ki67, ER, PR, HER2, and negative status for ER, PR, and HER2 (TN), yielded tumor grade and ER status as independent predictors of pCR (p < 0.004). The gene discussed is ESR1; the disease is breast cancer.