The prostate is organized as a classical exocrine gland and is composed of a complex array of ductal-acinar structures embedded in stroma. The ducts and acini are lined by the secretory and nonsecretory epithelial cells, whereas stroma comprises of smooth muscle cells, fibroblasts, and blood vessels. The major secretory cells in the prostate are the luminal epithelial cells, which face the lumen of ducts and acini and supply approx 30% of the seminal fluid components. The nonsecretory epithelial cells, called basal epithelial cells, lie below the luminal epithelial cells and rest on the basement membrane, which separates the prostatic epithelium from the surrounding stroma (1 ,2 ). The luminal epithelial cells are highly differentiated cells that express prostatespecific antigen (PSA; ref. 3 –7 ), cytokeratins 8 and 18 (8 ,9 ), and the nuclear androgen receptor (AR; ref. 2 and 10 ). In contrast to luminal epithelial cells, basal epithelial cells do not express PSA and AR but express cytokeratins 5 and 14 (8 ,9 ), P-cadherin (11 ), Bcl2 (12 ), and c-met (13 ,14 ). The function of basal epithelial cells during prostate morphogenesis is unknown, although a putative stem cell role has been suggested (15 ). Although prostatic epithelium is formed of two major compartments comprising basal and luminal cells, it also contains a minor component of cells of unknown function with distinct neuroendocrine characteristics, which can be distinguished from surrounding epithelial cells as they express neuroendocrine markers, such as chromagranin A and neurone-specific enolase (16 ,17 ). The smooth muscle cells, fibroblasts, and the endothelial cells in the blood vessels of prostate stroma can be distinguished from one