Decreased infiltration of macrophage scavenger receptor‐positive cells in initial negative biopsy specimens is correlated with positive repeat biopsies of the prostate

Macrophage scavenger receptor (MSR)‐positive inflammatory cells and tumor‐associated macrophages (TAMs) have been reported to regulate the growth of various cancers. In this study, the infiltration of MSR‐positive cells and TAMs was analyzed to predict the outcome of repeat biopsy in men diagnosed as having no malignancy at the first prostate biopsy. Repeat biopsy of the prostate was carried out in 92 patients who were diagnosed as having no malignancy at the first biopsy. Of these, 30 patients (32.6%) were positive for prostate cancer at the repeat biopsy. Tumor‐associated macrophages and MSR‐positive cells were immunohistochemically stained with mAbs CD68 and CD204, respectively. Six ocular measuring fields were chosen randomly under a microscope at ×400 power in the initial negative biopsy specimens, and the mean TAM and MSR counts for each case were determined. No difference in TAM count was found between the cases with or without prostate cancer. By contrast, the MSR count in patients with cancer was significantly lower than that in patients without cancer at the repeat biopsy (P < 0.001). Logistic regression analysis indicated that the MSR count at first biopsy is a significantly better predictive factor for positive repeat biopsy than PSA velocity, interval between first and repeat biopsies, or TAM count. Decreased infiltration of MSR‐positive cells in negative first biopsy specimens was correlated with positive findings in the repeat biopsy. The MSR count might be a good indicator for avoiding unnecessary repeat biopsies. (Cancer Sci 2010)