The prostate, found only in males, is a walnut-sized gland located in front of the rectum and underneath the urinary bladder. It contains glandular cells that make some of the fluid that protects and nourishes sperm cells in semen. Several cell types are found in the prostate, but over 99% of prostate cancers develop from the glandular cells.
While some prostate cancers can grow and spread quickly, most prostate cancers grow slowly. In fact, autopsy studies show that many older men who died of other diseases also had prostate cancer that never affected them and had remained undetected throughout their lives.
Prostate cancer is often asymptomatic. In men who do have symptoms, common symptoms include urinary problems, difficulty having an erection, blood in the urine or semen, and frequent pain in the lower back, hips or upper thighs. However, overall, these symptoms are more likely due to benign prostatic hypertrophy (BPH), infections, or other health problems than they are to cancer. It is thought that prostate cancer might begin with a condition called prostatic intraepithelial neoplasia (PIN). PIN begins to appear in some men in their 20s. Almost half of men have PIN by the time they reach 50. In this condition, there are changes in the microscopic appearance (size, shape, etc.) of prostate gland cells. These changes are classified as either low grade, meaning they appear almost normal or high grade, meaning they look abnormal. If a high-grade PIN is diagnosed on a prostate biopsy, there is a 33% or higher chance that there is cancer in the prostate. For this reason, men diagnosed with high-grade PIN are often watched carefully and have repeat prostate biopsies.