The prostate is a gland of the male reproductive system that produces fluid for semen, which helps to transport sperm during the male orgasm. The prostate is made up of about 30% muscular tissue; the rest is glandular tissue.

Normally, the prostate is small—about the same size and shape as a walnut. It is located in front of the rectum and just below the bladder. The prostate wraps around the urethra, which is the tube that carries urine out from the bladder through the tip of the penis.

To get a better picture of what prostate cancer looks like compared to a healthy prostate gland, see Grading and Staging, What the Numbers Mean.

Read more about prostate related diseases.