In prostate cancers, PSA staining was seen in 99.9–100% (1:800–1:100) primary tumors, 98.7–99.7% of advanced recurrent cancers, in 84.6–91.4% castration resistant cancers, and in 7.7–18.8% of 16 small cell carcinomas. The gene discussed is KLK3; the disease is prostate cancer.