Histology and distribution of prostatic tissue on prostatic urethral margins: evaluation of radical prostatectomy specimens and implications on frozen section analysis.

The identification of prostate-specific antigen (PSA)-producing glands in prostatic urethral margins is often challenging, especially when examined as intraoperative frozen sections. To assess the histology of periurethral prostatic urethral glands and their expression of PSA and cytokeratins 7 and 20, we examined prostatic urethras of frozen and permanent sections of radical prostatectomy specimens. We observed 3 types of prostatic urethral glands: urethral mucosal, prostatic acinar, and mixed. The urethral mucosal type consisted of a single layer of surface cuboidal to columnar cells with densely eosinophilic luminal cytoplasm and underlying urothelial cells. The prostatic acinar type was lined by prostatic-type secretory cells and basal cells. The mixed type showed luminal secretory cells and underlying urothelial cells. The gland types were correctly assigned in most frozen section slides. The proximal segment of the prostatic urethra and the bladder neck consisted mostly of the urethral mucosal type, whereas the distal segment and apical margins consisted mostly of the prostatic acinar type. Prostate-specific antigen was expressed in secretory cells in prostatic acinar and mixed types, whereas cytokeratin 7 was expressed by urothelial cells and surface cells of the urethral mucosal type. Cytokeratin 20 was not expressed in any of these cells. These results indicate that PSA-expressing cells are abundant in the distal segment of the prostatic urethra and apical margin and share histologic features of prostatic secretory cells. These PSA-expressing prostatic acinar and mixed-type glands should be reported as a potential source of PSA-secreting benign glands.