High-Grade Prostatic Intraepithelial Neoplasia

Abstract

Prostatic intraepithelial neoplasia (PIN) is considered a precursor lesion to prostate carcinoma and a surrogate marker for cancer in prostate biopsies. It is characterized by secretory epithelial proliferation within the prostate glands and acini that display significant cytological atypia. PIN does not result in an abnormal digital rectal examination nor elevated serum prostate-specific antigen (PSA) level and can only be diagnosed by histological examination of the prostate tissue. Based on the degree of atypia, PIN can be categorized into low-grade (LGPIN) and high-grade PIN (HGPIN). The significance of a PIN diagnosis in biopsy is the cancer risk in follow-up repeat biopsies. LGPIN is not associated with increased cancer detection in follow-up repeat biopsies, and its diagnosis is not readily reproducible even among urologic pathologists; therefore, it should not be diagnosed and reported in prostate biopsy. The clinical significance and management of HGPIN diagnosed in needle biopsy have drastically changed in the last decade. The diagnosis carries a 20–30% cancer risk in subsequent biopsies, which is not significantly higher than the cancer risk associated with a benign or LGPIN diagnosis. Therefore, men with HGPIN involving a single biopsy core should be followed similar to men with benign results and do not need repeat biopsy. Men with HGPIN involving multiple cores have an increased risk of cancer compared with those with a benign or unifocal HGPIN. These patients are recommended for additional serum and urine biomarker testing and imaging studies to assess the risk of high-grade cancer, and the decision to perform repeat biopsy depends upon such risk assessment.