Prognostic impact of a tumor-infiltrating lymphocyte subtype in triple negative cancer of the breast

Background Tumor-infiltrating lymphocytes (TILs) have recently been reported as an important factor in the tumor microenvironment and influence the growth and progression of cancer. However, the relationship between immune cell subpopulations, such as CD4+, CD8+, and FOXP3+, in breast cancer, especially in triple negative carcinoma (TNC), remains unclear. Methods The subjects were 107 patients with TNC that were surgically resected at Dokkyo Medical University Hospital between 2006 and 2018. The expression of CD4+, CD8+, and FOXP3+ was evaluated in TILs and expressed as the numbers of positive cells. Results Univariate analysis revealed that the TILs were not prognostically significant. In multivariate analyses, increased infiltration of intratumoral (i) CD4+ TILs was found to have a good prognosis in relapse-free survival (RFS). In contrast, a high stromal CD8+ TILs level was found to be a favorable prognostic factor in RFS (p = 0.038) and overall survival (OS) (p = 0.046). A low sFOXP3 + TILs level was significantly associated with favorable RFS (p < 0.001) and OS (p = 0.029). Conclusions The present study demonstrated no difference in TILs and survival in TNC. However, there was a significant correlation in prognosis with levels of iCD4+, sCD8+, and sFOXP3 + TILs in TNC. The difference in TNC clinical outcome may be due to the subtype of the infiltrating TILs.