PSA-negative tumours of the prostate

The immunoperoxidase staining of normal and hyperplastic prostatic epithelium for Prostate Specific Antigen (PSA) is, with few exceptions, uniform and strong. In contrast to the benign tissue, most reports of prostatic adenocarcinoma demonstrated an apparent correlation between staining-variability and increasing tumour grades. Decreased PAP staining may be related to incorrect manipulation of prostatic tissue. Finally there are many tumours and pseudotumours of the prostate in which the PSA stain is regularly negative. In the differential diagnosis of prostate tumour, both PSA and PAP (Prostatic Acid Phosphatase) stains should be performed. It is mandatory that the stains be interpreted in the appropriate histologic and clinicopathologic setting with due consideration of positive and negative staining.