Reelin is a glycoprotein that plays a critical role in the regulation of neuronal migration during brain development and, since reelin has a role in the control of cell migration, it might represents an important factor in cancer pathology. In this study, 66 surgical specimens of prostate cancer were analyzed for reelin expression by immunohistochemical method. The reelin expression was correlated with Gleason score and individual Gleason patterns. Reelin expression was found in 39% prostate cancers. Stromal tissues, normal epithelial cells and prostate intraepithelial neoplasia (PIN) of any grade around and distant from cancer were always negative for reelin. Reelin was found in malignant prostatic epithelial glands of 50% cases Gleason score 10, 52% Gleason score 9, 56% Gleason score 8, 18% Gleason score 7, while no sample of prostate cancers with Gleason score 6 showed reelin expression (P=0,005). As reelin staining is frequently found in high Gleason score prostate cancers, we explored whether reelin expression is influenced by single Gleason patterns. While Gleason 3 pattern did not show reelin immunoreactivity, reelin expression was found in 35% Gleason 4 patterns and 45% Gleason 5 patterns (P<0.001). Our results demonstrated for the first time that reelin is expressed in prostate cancer and not in benign prostate tissue and its expression occurs in higher Gleason score and correlates significantly with increasing of single Gleason patterns. This suggests reelin may behave as a specific histological marker and may represent a useful biomarker to predict aggressive phenotypic behavior of prostatic cancer cells.