The results of the present study suggest that PTX3 expression within an inflamed prostate is quantitatively, temporarily and spatially correlated with C1q expression, suggesting the activation of classical pathway of the complement system without resulting in C5b-9 activation; finally, PTX3-associated C1q deposits along with CD59, C3aR and C5aR1 increased expression, are strictly correlated with the subsequent development of prostate cancer. This evidence concerns the gene C5AR1 and prostate cancer.