The prostate, found only in men, is a walnut-sized gland located in front of the rectum, at the outlet of the bladder. It contains gland cells that produce some of the seminal fluid, which protects and nourishes sperm cells in semen. Just behind the prostate gland are the seminal vesicles that produce most of the fluid for semen. The prostate surrounds the first part of the urethra, the tube that carries urine and semen through the penis. Male hormones stimulate the prostate gland to develop in the fetus. The prostate continues to grow as a man reaches adulthood. It will continue to grow or at least is maintained after it reaches normal size throughout the life of a man as long as male hormones are produced. If male hormones are removed, the prostate gland will not fully develop or will shrink. .
Although several other cell types are found in the prostate, over 99% of prostate cancers develop from the glandular cells. The medical term for a cancer that starts in glandular cells is adenocarcinoma. Because other types of prostate cancer are so rare, if you have prostate cancer, it is almost certain to be adenocarcinoma. .
Most prostate cancers grow very slowly. Autopsy studies show that many elderly men who died of other diseases also had a prostate cancer that neither they nor their doctor were aware of. Some prostate cancers, however, can grow and spread quickly. .
Many doctors believe that prostate cancer begins with a condition called prostatic intraepithelial neoplasia (PIN). In this condition there are precancerous changes in the microscopic appearance (the size, shape, or the rate at which they multiply) of prostate gland cells. This condition begins to appear in men in their 20's and by the time they reach 50, almost 50% of men have PIN. Cancer may occur about 10 to 20 years after the PIN develops. PIN can be either low grade or high grade. If you have high-grade PIN, cancer is likely to develop and your condition should be watched carefully.