Prognostic Value of Tumor-Infiltrating B Lymphocytes and Plasma Cells in Triple-Negative Breast Cancer

Recent investigations have demonstrated that the tumor microenvironment, including tumor-infiltrating lymphocytes (TILs), is an important factor in tumor growth and development. While the prognostic correlation of tumor-infiltrating T cells has been widely studied in breast cancer, that of tumor-infiltrating B cells and plasma cells has not received so much attention, especially in triple-negative breast cancer (TNBC). We investigated 114 patients with TNBC who had surgery between 2006 and 2019 at Dokkyo Medical University Hospital. Intratumoral (i) TILs were considered to be lymphocytes within cancer cell nests and directly infiltrating tumor cells. Similarly, stromal (s) TILs were considered to be lymphocytes within the tumor stroma, but not directly infiltrating tumor cells. CD20 + , CD38 + and CD138 + staining was determined by estimating the number of positive B cells. sCD20 + TILs had prognostic significance for relapse-free survival (RFS) (p = 0.043) and overall survival (OS) (p = 0.027). The sCD38 + TILs were significantly related to favorable RFS (p = 0.042). iCD38, iCD138, and sCD138 was not significantly correlated with RFS (p = 0.065, p = 0.719, p = 0.074) or OS (p = 0.071, p = 0.689, p = 0.082). The present study demonstrated that a high density of sCD20 + TILs was significantly related to favorable prognosis in both RFS and OS. Increased sCD38 + TILs in TNBC were correlated with a significantly favorable prognosis in RFS. These results indicate that TILs–B may have a profound influence on the clinical outcome of TNBC.