Using this FISH method, early studies by Yoshimoto et al. (23) analyzing 35 radical prostatectomy specimens showed no PTEN deletion in benign glandular epithelium or low-grade Prostatic Intra-epithelial Neoplasia (PIN), while PTEN deletions were found in 23% of High-Grade Prostatic Intra-epithelial Neoplasia (HGPIN), a pre-malignant stage of prostate carcinoma, and 68% of overt prostate cancer. This evidence concerns the gene PTEN and Familial prostate cancer.