Tumor-associated macrophages predict prognosis in diffuse large B-cell lymphoma and correlation with peripheral absolute monocyte count

BACKGROUND: Diffuse large B-cell lymphoma (DLBCL) is characterized by its clinical and biological heterogeneity. The clinical prognostic implications of tumor-associated macrophages (TAMs) in DLBCL remain controversial and the correlation between TAMs and peripheral absolute monocyte count (AMC) has not yet been elucidated. METHODS: In 221 untreated, newly diagnosed patients with DLBCL, we evaluated the prognostic value of TAMs using immunohistochemical analysis, as well as the association of TAMs and AMC. RESULTS: We found that high CD68 or high CD163 expression was correlated with clinicopathological characteristics, high CD163 expression was an adverse predictor for both overall survival (OS) [hazard ratio (HR) = 2.265, P = 0.005] and progression- free survival (PFS) (HR = 1.925, P = 0.017) in patients with DLBCL. Patients with high CD68 or high CD163 expression had significantly poorer OS and PFS than those with low CD68 or low CD163 expression, respectively (CD68: OS: P<0.001, PFS: P<0.001; CD163: OS: P<0.001, PFS: P<0.001), even in the rituximab era. Moreover, high-risk patients could be further identified by the expression of CD68 or CD163, especially in those classified as low/intermediate risk by International Prognostic Index (IPI). Furthermore, the significant positive correlation was also detected between CD68 expression or CD163 expression and AMC (r = 0.256, P<0.001; r = 0.303, P<0.001). CONCLUSIONS: Patients with high expression of TAMs tend to have poorer OS and PFS, even in the rituximab era, and have positive correlation with AMC. Therefore, the peripheral AMC is a useful prognostic marker reflecting the status of the tumor microenvironment (TME) in DLBCL.