To determine the clinical relevance of ERα in prostate cancer, we performed immunohistochemistry using a tissue microarray composed of tissue cores from 64 samples of benign prostate tissue, 16 high-grade prostate intraepithelial neoplasia, 292 PCa, and 42 neuroendocrine prostate cancer (NEPC). The gene discussed is ESR1; the disease is prostate intraepithelial neoplasia.