What to Know About a Prostate Biopsy

Medically Reviewed

If the results of your digital rectal exam, prostate-specific-antigen (PSA) test, or both, suggest cancer, your doctor will ask for a transrectal ultrasound-guided biopsy. That will determine the size of the prostate, identify any areas that are suspicious for cancer, and direct the needles to be used for a prostate biopsy, which typically takes about 15 to 20 minutes and is performed on an outpatient basis.

What to expect

Doctors routinely use a local anesthetic such as lidocaine (Xylocaine) to reduce discomfort during a prostate biopsy. The biopsy is performed with you lying on your side. The ultrasound probe (about the size of a finger) is gently inserted 3 to 4 inches into the rectum. The probe emits sound waves that are converted into images corresponding to the different prostate zones.

Small prostate cancers are usually not detectable by ultrasound examination. Fitted to the probe is a biopsy gun with a needle that is fired through the wall of the rectum. The needle extracts small pieces of prostate tissue in less than a second.

Ideally, at least 10 to 12 tissue samples (“cores”) are taken from the prostate. A pathologist examines the samples under a microscope to determine whether cancer is present.

If the prostate biopsy shows no cancer but the physician still suspects that cancer is present because of an abnormality on the digital rectal exam or PSA test, a repeat biopsy may be performed.

Possibility of cancer

Each year, approximately 1 million prostate biopsies are performed in the U.S., and of those, about 1 in 3 are cancerous. About 5 to 10 percent of men who have had a biopsy will be told they have high-grade prostatic intraepithelial neoplasia (PIN).

Formerly called dysplasia or atypical hyperplasia, PIN is believed to be a premalignant lesion. But recent studies suggest that the likelihood of finding cancer on a repeat biopsy is no greater in men with PIN than in men with normal biopsy findings. Therefore, a finding of PIN alone is not a reason to perform a repeat biopsy.

About 5 percent of prostate biopsies reveal abnormal or atypical cells that suggest the possibility of cancer but are not sufficient to make a diagnosis. In such cases, a repeat biopsy is usually recommended because there is a 50 percent chance of finding cancer on that second biopsy. If the biopsy results indicate cancer, other tests may need to be conducted to determine the extent of the disease.

A prostate biopsy usually causes only minor discomfort, but there is a small risk of infection. Common side effects include minor rectal bleeding; blood in the stool, urine, or semen; and soreness in the biopsied area. All of these side effects disappear with time.