&NA;This report illustrates common features of prostatic intraepithelial neoplasia (PIN), in which benign glands exhibit epithelial proliferation with tufting, micropapillary, cribriform, and flat patterns. High‐grade PIN is characterized by nuclear and nucleolar enlargement and differentiated from adenocarcinoma by the absence of stromal invasion and retention of the basal cell layer. In contrast to atypical basal cell hyperplasia, high‐grade PIN usually involves larger acini with full‐thickness epithelial atypia. Low‐grade PIN has architectural patterns similar to those of high‐grade PIN, but shows smaller and less frequent nucleoli. The presence of high‐grade PIN in the biopsy is a strong predictor of concurrent cancer and warrants further search for invasive carcinoma. Low‐grade PIN is not a predictor of carcinoma. For this reason and also because low‐grade PIN has poor diagnostic reproducibility, many pathologists choose not to report low‐grade PIN in biopsies.