The prostate can be divided into biologically distinct regions, the most important of which are the peripheral and transition zones (
Fig. 18.10 ). The types of proliferative lesions are different in each region. For example, most hyperplastic lesions arise in the inner transition zone, while most carcinomas (70%–80%) arise in the peripheral zones. As a result, carcinomas are often detected by rectal exammination, whereas hyperplasias are more likely to cause urinary obstruction. The normal prostate contains glands with two cell layers, a flat basal cell layer and an overlying columnar secretory cell layer. Surrounding prostatic stroma contains a mixture of smooth muscle and fibrous tissue. The prostate is involved by infectious, inflammatory, hyperplastic, and neoplastic disorders, of which prostate cancer is by far the most important clinically.
Fig. 18.10 Adultprostate.Thenormalprostatecontainsseveraldistinctregions,includingacentralzone(CZ),aperipheralzone(PZ),atransitionalzone(TZ),andaperiurethralzone.Mostcarcinomasarisefromtheperiph-eralglandsoftheorgan,whereasnodularhyperplasiaarisesfrommorecentrallysituatedglands.BladderProximal urethra Anterior fibromuscular stroma Periurethral zone Distal urethra CZTZTZPZCZSeminal vesicle Ejaculatory duct Rectum
Prostatitis is divided into three categories: (1) acute bacterial prostatitis (2%–5% of cases), caused by the same organisms associated with other acute urinary tract infections; (2) chronic bacterial prostatitis (2%–5% of cases), also caused by common uropathogens; and (3) chronic pelvic pain syndrome (90%–95% of cases). The latter can be subdivided into inflammatory cases, which are associated with leukocytes in prostatic secretions, and noninflammatory cases, in which leukocytes are absent.
The diagnosis of prostatitis is not typically based on biopsy, as the histologic findings are nonspecific and biopsy of an infected prostatitis can result in sepsis. The exception is granulomatous prostatitis, which may produce prostatic induration, leading to biopsy to rule out prostate cancer. In the United States, the most common cause of granulomatous prostatitis is instillation of Bacille Calmette-Guérin (BCG) within the bladder for treatment of superficial bladder cancer. BCG is an attenuated tuberculosis strain that produces a granulomatous immune reaction that is histologically indistinguishable from tuberculosis. Prostatic tuberculosis also occurs but is rare in the Western world. Fungal granulomatous prostatitis is typically seen only in immunocompromised hosts. Nonspecific granulomatous prostatitis is relatively common and stems from a foreign-body reaction to fluids that leak into tissue from ruptured prostatic ducts and acini. Postsurgical prostatic granulomas also may be seen.
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