Over-diagnosis of high-grade prostatic intraepithelial neoplasia: a prospective study of 251 cases.

OBJECTIVE To assess the magnitude and causes of over-diagnosis of prostatic intraepithelial neoplasia (PIN), as large differences are reported in the incidence of high-grade PIN, probably because of the variance in diagnosis and interpretation. PATIENTS AND METHODS Two urological pathologists prospectively reviewed 251 consecutive patients, received in consultation and who were diagnosed and finalized by outside pathologists as having PIN. RESULTS The diagnosis of PIN was confirmed in 191 patients (incidence of concordance 76.1%, true positive) and refuted in 60 (discordance 23.9%, false positive). The most common histopathological findings misinterpreted as PIN included basal cell hyperplasia, benign epithelium, low-grade PIN, reactive changes, cribriform hyperplasia, atrophy, and post-atrophic hyperplasia. CONCLUSIONS There is a high rate of over-diagnosis of PIN, usually by misinterpretation of benign mimics. This significant error rate might account for some of the reported differences in the incidence of PIN and the variable predictive accuracy for cancer.