AIM To determine influence of neoadjuvant-chemotherapy(NAC) over tumor-infiltrating-lymphocytes(TIL) intriple-negative-breast-cancer(TNBC).METHODS TILs were evaluated in 98 TNBC cases who came to Instituto Nacional de Enfermedades Neoplasicas from 2005 to 2010. Immunohistochemistry staining for CD3, CD4, CD8 and FOXP3 was performed in tissue microarrays(TMA) sections. Evaluation of H/E in full-face and immunohistochemistry in TMA sections was performed in pre and post-NAC samples. STATA software was used and P value < 0.05 was considered statistically significant. RESULTS Higher TIL evaluated in full-face sections from pre-NAC tumors was associated to pathologic-complete-response(pCR)(P = 0.0251) and outcome(P = 0.0334). TIL evaluated in TMA sections showed low level of agreement with full-face sections(ICC = 0.017-0.20) and was not associated to pCR or outcome. TIL in post-NAC samples were not associated to response or outcome. PostNAC lesions with pC R had similar TIL levels than those without pCR(P = 0.6331). NAC produced a TIL decrease in full-face sections(P < 0.0001). Percentage of TIL subpopulations was correlated with their absolute counts. Higher counts of CD3, CD4, CD8 and FOXP3 in pre-NAC samples had longer disease-free-survival(DFS). Higher counts of CD3 in pre-NAC samples had longer overallsurvival. Higher ratio of CD8/CD4 counts in pre-NAC was associated with pCR. Higher ratio of CD4/FOXP3 counts in pre-NAC was associated with longer DFS. Higher counts of CD4 in post-NAC samples were associated with pCR.CONCLUSION TIL in pre-NAC full-face sections in TNBC are correlated to longer survival. TIL in full-face differ from TMA sections, absolute count and percentage analysis of TIL subpopulation closely related. AIM To determine influence of neoadjuvant-chemotherapy (NAC) over tumor-infiltrating-lymphocytes (TIL) intriple-negative-breast-cancer 2010. Immunohistochemistry staining for CD3, CD4, CD8 and FOXP3 was performed in Tissue microarrays (TMA) sections. Evaluation of H / E in full-face and immunohistochemistry was performed in pre and post-NAC samples. STATA software was used RESULTS Higher TIL evaluated in full-face sections from pre-NAC tumors was associated to pathologic-complete-response (pCR) (P = 0.0251) and outcome (P = 0.0334). TIL evaluated in TMA sections showed low level of agreement with full-face sections (ICC = 0.017-0.20) and was not associated to pCR or outcome. TIL in post-NAC samples were not associated to response or outcome. TIL levels than tho Percentage of TIL subpopulations was correlated with their absolute counts. Higher counts of CD3, CD4, CD8 and FOXP3 in pre-NAC (P = 0.6331). NAC produced a TIL decrease in full- Higher counts of CD3 in pre-NAC samples had longer overall svrevival. Higher ratio of CD8 / CD4 counts in pre-NAC was associated with pCR. Higher ratios of CD4 / FOXP3 counts in pre -NAC was associated with longer DFS. Higher counts of CD4 in post-NAC samples were associated with pCR.CONCLUSION TIL in pre-NAC full-face sections in TNBC are correlated to longer survival. TIL in full-face differ from TMA sections, absolute count and percentage analysis of TIL subpopulation closely related.