An increase of M2 macrophages predicts poor prognosis in patients with diffuse large B-cell lymphoma treated with rituximab, cyclophosphamide, doxorubicin, vincristine and prednisone.

Tumor-associated macrophages (TAMs) and regulatory T-cells (Tregs) play an important role in the tumor microenvironment. Here, we investigated the prognostic implications of TAMs and Tregs in 165 diffuse large B-cell lymphomas (DLBCLs) using immunohistochemistry. Survival analysis was performed among 109 DLBCLs treated with rituximab, cyclophosphamide, doxorubicin, vincristine and prednisone (R-CHOP). An increase in CD68 (+) cells was related to improved overall survival (OS) (p = 0.033). By contrast, an increased number of CD163 (+) cells and a higher ratio of CD163/CD68 (+) cells were significantly associated with shorter OS (p = 0.041 and 0.003) and progression-free survival (PFS) (p < 0.001 and 0.002). Patients with increased Tregs tended to have a better prognosis. In multivariate analysis, an increased ratio of CD163/CD68 (+) cells was an independent predictor of shorter OS and PFS. These results suggest that M2 macrophages might have a lymphoma-promoting function in DLBCL and predict poor clinical outcome. Therapeutic approaches targeting M2 macrophages would be valuable for the management of DLBCL in the R era.