The distribution of S-100 protein in hyperplastic and neoplastic prostatic epithelium.

Specimens from 30 cases of benign prostatic hyperplasia and 75 cases of prostatic carcinoma obtained during suprapubic prostatectomy, transurethal resection of the prostate and radical prostatectomy, were stained immunohistochemically for S-100 protein, prostatic acid phosphatase (PAP), prostatic specific antigen (PSA), neuron specific enolase (NSE) and polyclonal keratin. S-100 protein was positive in 9.3% of prostatic carcinomas and negative in all cases of prostatic hyperplasia. PAP and PSA were positive in all cases, while NSE was positive in 16% of the carcinoma cases. Polyclonal keratin was positive in both cell layers of the double layered hyperplastic prostatic epithelium with a more intense staining pattern in the outer cell layer. The authors believe that the S-100 protein immunoreactivity observed in some prostatic carcinomas, reflecting the change in the functional status of the neoplastic cells, might be of prognostic significance. They also emphasize the non-myoepithelial nature of the outer cell layer of the double layered prostatic epithelium.