Cytokeratin immunohistochemistry as a diagnostic tool for distinguishing malignant from benign epithelial lesions of the prostate.

The basal cell layer (BCL) is believed to be absent in malignant but present in nonmalignant epithelial lesions of the prostate. Using the avidin-biotin-peroxidase complex (ABC) immunoperoxidase method, we examined the value of the monoclonal antibody cocktail MA-903, which stains selectively the prostatic BCL layer, in the distinction between benign and malignant epithelial lesions of the prostate. We immunostained histologic sections of 63 prostates, containing 235 morphologic appearances: normal prostate glands, 43; benign prostate hyperplasia (BPH), 59; basal cell hyperplasia (BCH), 24; adenosis, seven; prostatic intraductal neoplasia (PIN 1), 21; PIN 2, 25; PIN 3, 16; and cancer, 40. Some degree (continuous, continuous with focal disruption, and disrupted patterns) of basal cell staining was demonstrable in all normal and BPH, BCH, and PIN 1 lesions, but was absent in 39 of 40 cancers. However, not every gland in benign lesions stained positively. Further, two of 25 PIN 2 and six of 16 PIN 3 lesions failed to reveal BCL. Our results suggest that the presence or absence of BCL, predicated on cytokeratin MA-903 immunoreactivity, may be a useful indicator in the distinction between benign and malignant epithelial lesions of the prostate.