For many tumors the early detection of precursor lesions of invasive cancer has an impact on the clinical course. The high-grade prostatic intraepithelial neoplasia (HG-PIN) is the only accepted facultative precursor lesion for acinar prostate cancer. While HG-PIN shows many similarities to prostate cancer it is most probably not a precursor of every prostate cancer variant. However, the detection of HG-PIN in needle biopsies is a significant risk factor for the subsequent diagnosis of invasive prostate cancer. Low-grade PIN (LG-PIN), proliferative inflammatory atrophy (PIA), and atypical adenomatous hyperplasia are no longer considered to be true precursor lesions.