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What Is Prostate Cancer?

A diagram showing the location of the prostate.

This diagram shows the location of the prostate, in front of the rectum and just below the bladder.

Cancer is a disease in which cells in the body grow out of control. When cancer starts in the prostate, it is called prostate cancer. Except for skin cancer, prostate cancer is the most common cancer in American men.

What Is the Prostate?

The prostate is a part of the male reproductive system, which includes the penis, prostate, and testicles. The prostate is located just below the bladder and in front of the rectum. It is about the size of a walnut and surrounds the urethra (the tube that empties urine from the bladder). It produces fluid that makes up a part of semen.

As a man ages, the prostate tends to increase in size. This can cause the urethra to narrow and decrease urine flow. This is called benign prostatic hyperplasia, and it is not the same as prostate cancer. Men may also have other prostate changes that are not cancer.

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