Macrophage Infiltration in Tumor Stroma is Related to Tumor Cell Expression of CD163 in Colorectal Cancer

The scavenger receptor, CD163, is a macrophage-specific marker. Recent studies have shown that CD163 expression in breast and rectal cancer cells is associated with poor prognosis. This study was conducted to evaluate the relationship between CD163 expression as a macrophage trait in cancer cells, and macrophage infiltration and its clinical significance in colorectal cancer. Immunostaining of CD163 and macrophage infiltration were evaluated in paraffin-embedded specimens, earlier analyzed for CD31, D2-40 and S-phase fraction, from primary tumors and normal colorectal mucosa of 75 patients with colorectal carcinoma. The outcomes were analyzed in relation to clinical-pathological data. CD163 expression was positive in cancer cells in 20 % of colorectal cancer patients and was related to advanced tumor stages (P = 0.008) and unfavorable prognosis (p = 0.001). High macrophage infiltration was related to shorter survival and positive CD163 expression in tumor cells. The prognostic impact of macrophage infiltration was independent of tumor stage and CD163 expression in cancer cells (p = 0.034). The expression of macrophage phenotype in colorectal cancer cells is associated with macrophage density in tumor stroma and lower survival rates. Macrophage infiltration has an independent prognostic impact on mortality in colorectal cancer. In accordance with previous experimental studies, these findings provide new insights into the role of macrophages in colorectal cancer.