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The prostate

The prostate gland is found only in males. It is just below the bladder and in front of the rectum. The tube that carries urine (the urethra) runs through the center of the prostate. The prostate contains cells that make some of the fluid (semen) that protects and nourishes the sperm.

The size of the prostate changes with age. In younger men, it is about the size of a walnut, but it can be much larger in older men. The growth is fueled by male hormones (called androgens) such as testosterone.

Benign prostatic hyperplasia (BPH)

BPH is a condition that causes the prostate to get larger as men age. BPH is not cancer and does not change into cancer. But it can cause problems urinating if the prostate gets large enough to press on the urethra. BPH is often treated with drugs that shrink the prostate or relax the muscles in it, which can help urine flow. If drugs aren’t helpful, some type of surgery, such as a transurethral resection of the prostate (TURP) may be needed. (See the “Surgery for prostate cancer” section for a description of this procedure.)

Prostate cancer

Cancer starts when cells in the body begin to grow out of control. Cells in nearly any part of the body can become cancer, and can spread to other areas of the body. To learn more about how cancers start and spread, see What Is Cancer?

There are several types of cells in the prostate, but nearly all prostate cancers start in the gland cells. This kind of cancer is known as adenocarcinoma. The rest of the information here refers only to prostate adenocarcinoma.

Some prostate cancers can grow and spread quickly, but most of the time, prostate cancer grows slowly. Autopsy studies show that many older men (and even some younger men) who died of other causes also had prostate cancer that never caused them problems. In many cases neither they nor their doctors even knew they had it.

Possible pre-cancerous changes of the prostate

Some research suggests that prostate cancer starts out with very small changes in prostate gland cells, although this is not known for sure.

Prostatic intraepithelial neoplasia (PIN)

In PIN, there are changes in how the prostate gland cells look under the microscope, but the cells don’t look like they’ve gone into other parts of the prostate (like cancer cells would). Almost half of all men have PIN by the time they reach age 50.

  • In low-grade PIN, the cells look almost normal. There usually is no reason to be concerned about this condition. For men with low-grade PIN, follow-up is most often the same as if nothing abnormal was seen.
  • In high-grade PIN, the cells look more abnormal. This is more concerning because men with high-grade PIN have about a 20% chance of having cancer in another part of the prostate. This is why doctors often watch men with high-grade PIN carefully and may advise them to have a repeat prostate biopsy.

Proliferative inflammatory atrophy (PIA)

This is another possible finding on a prostate biopsy. In PIA, the prostate cells look smaller than normal, and there are signs of inflammation in the area. PIA is not cancer, but researchers believe that PIA may sometimes lead to high-grade PIN, or perhaps to prostate cancer.

Last Medical Review: 01/09/2015
Last Revised: 02/09/2016