Second, this simplified diagnostic assay can be used for accurate diagnosis of the malignant potential of prostate cancer at the pre-malignant (PIN) stage before becoming a frank malignant cancer (namely a metastatic cancer), which is different from the PSA test, suggesting that METCAM/MUC18 appears to have the advantage over the PSA test in early detection of the malignant potential of prostate cancer. Here, MCAM is linked to prostate cancer.