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The prostate gland is the male organ most commonly afflicted with either benign or malignant neoplasms. McNeal et al (1988) popularized the concept of zonal anatomy of the prostate. Three distinct zones have been identified (Figure 23–1). The peripheral zone accounts for 70% of the volume of the young adult prostate, the central zone accounts for 25%, and the transition zone accounts for 5%. These anatomic zones have distinct ductal systems but, more important, are differentially afflicted with neoplastic processes. Sixty to seventy percent of carcinomas of the prostate (CaP) originate in the peripheral zone, 10–20% in the transition zone, and 5–10% in the central zone (McNeal et al, 1988). Benign prostatic hyperplasia (BPH) uniformly originates in the transition zone (Figure 23–2).
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Incidence and Epidemiology
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BPH is the most common benign tumor in men, and its incidence is age related. The prevalence of histologic BPH in autopsy studies rises from approximately 20% in men aged 41–50, to 50% in men aged 51–60, and to >90% in men older than 80 years. Although clinical evidence of disease occurs less commonly, symptoms of prostatic obstruction are also age related. At age 55, approximately 25% of men report obstructive voiding symptoms. At age 75, 50% of men complain of a decrease in the force and caliber of their urinary stream.
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Risk factors for the development of BPH are poorly understood. Some studies have suggested a genetic predisposition, and some have noted racial differences. Approximately 50% of men younger than 60 years who undergo surgery for BPH may have a heritable form of the disease. This form is most likely an autosomal dominant trait, and first-degree male relatives of such patients carry an increased relative risk of approximately fourfold.
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The etiology of BPH is not completely understood, but it seems to be multifactorial and endocrine controlled. The prostate is composed of both stromal and epithelial elements, and each, either alone or in combination, can give rise to hyperplastic nodules and the symptoms associated with BPH. Each element may be targeted in medical management schemes.
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Observations and clinical studies in men have clearly demonstrated that BPH is under endocrine control. Castration results in the regression of established BPH and improvement in urinary symptoms. Additional investigations have demonstrated a positive correlation between levels of free testosterone and estrogen and the ...