['Tumor microenvironment immunity is associated with breast cancer outcome. A high lymphocytic infiltration has been associated with response to neoadjuvant chemotherapy, but the contribution to response and prognosis of immune cell subpopulations profiles in both pre-treated and post-treatment residual tumor is still unclear.', 'We analyzed pre- and post-treatment tumor-infiltrating immune cells (CD3, CD4, CD8, CD20, CD68, Foxp3) by immunohistochemistry in a series of 121 breast cancer patients homogeneously treated with neoadjuvant chemotherapy. Immune cell profiles were analyzed and correlated with response and survival.', 'We identified three tumor-infiltrating immune cell profiles, which were able to predict pathological complete response (pCR) to neoadjuvant chemotherapy (cluster B: 58%, versus clusters A and C: 7%). A higher infiltration by CD4 lymphocytes was the main factor explaining the occurrence of pCR, and this association was validated in six public genomic datasets. A higher chemotherapy effect on lymphocytic infiltration, including an inversion of CD4/CD8 ratio, was associated with pCR and with better prognosis. Analysis of the immune infiltrate in post-chemotherapy residual tumor identified a profile (cluster Y), mainly characterized by high CD3 and CD68 infiltration, with a worse disease free survival.'] Do tumor-infiltrating immune cell profiles and their change after neoadjuvant chemotherapy predict response and prognosis of breast cancer?