B cells in tertiary lymphoid structures are associated with favorable prognosis in gastric cancer.

BACKGROUND: The role of tumor-infiltrating B cells in the tumor microenvironment is still unclear. Recent studies have reported that B cells and tertiary lymphoid structures (TLSs) that contain B cell follicles correlate with the favorable prognosis of cancer patients. The aim of this study was to investigate the association between tumor-infiltrating B cells and clinicopathological features in gastric cancer.

METHODS: Tumor blocks were obtained from 226 patients with stage Ib to stage IV gastric cancer. The density of CD20(+) B cells within the tumor and in the invasive margin area was assessed using immunohistochemistry. We also evaluated CD3(+) T cells, CD21(+) follicular dendritic cells, Bcl6(+) germinal center B cells, and PNAd(+) high endothelial venules to show the presence of TLSs.

RESULTS: Tumor-infiltrating B cells were mostly organized as clusters that were surrounded by CD3(+) T cells. The B cell area contained follicular dendritic cells and some clusters contained Bcl6(+) B cells. High endothelial venules were present around follicles. We identified these follicles as TLSs. A high number of CD20(+) B cells were associated with significantly better overall survival, and multivariate analysis also showed that CD20 high was one of the independent predictors of prognosis. In addition, there was a significant correlation between CD20(+) B cell and CD8(+) T cell infiltration.

CONCLUSIONS: B cells mostly infiltrated tumors as TLSs and were associated with better prognosis in patients with gastric cancer.