Beltran L, et al. - Researchers sought the rate and causes of histopathologic false-positive diagnosis of prostate cancer. A panel of 3 genitourinary pathologists reviewed the diagnostic biopsies (n=1080) and transurethral resection of prostate specimens (n=314) from 1394 men with clinically localized prostate cancer diagnosed in the United Kingdom but treated conservatively between 1990 and 2003. For being potentially incomplete, 35 cases were excluded leaving 1359 cases in this study. Of these, 30 (2.2%) were reassigned to a nonmalignant category (26 benign and 4 suspicious for malignancy). On 7 of these, immunohistochemistry (IHC) had been originally performed. The errors were recorded due to the following reasons: adenosis (19), partial atrophy (3), prostatic intraepithelial neoplasia (2), seminal vesicle epithelium (1), and hyperplasia (1). These findings suggest that for a large proportion of the false-positive prostate cancer diagnoses, a relatively small number of prostate cancer mimics were responsible. The use of IHC was not identified preventing the overcall of benign entities as cancer in approximately a quarter of these cases. To lower the rate of false-positive diagnosis, they suggest targeting these mimics at educational events and raising awareness of the pitfalls in the interpretation of IHC in prostate cancer diagnosis, emphasizing that glands within a suspicious focus should be treated as a whole rather than individually.