If certain symptoms or the results of early detection tests -- the prostate-specific antigen (PSA) blood test and/or digital rectal exam (DRE) -- suggest that you might have prostate cancer, your doctor will do a prostate biopsy to find out if the disease is present.

The prostate biopsy

A biopsy is a procedure in which a sample of body tissue is removed and then looked at under a microscope. A core needle biopsy is the main method used to diagnose prostate cancer. It is usually done by a urologist, a surgeon who treats cancers of the genital and urinary tract, which includes the prostate gland. Using transrectal ultrasound (described in the section, "Can prostate cancer be found early?") to "see" the prostate gland, the doctor quickly inserts a needle through the wall of the rectum into the prostate gland. When the needle is pulled out it removes a small cylinder of tissue, usually about 1/2-inch long and 1/16-inch across. This is repeated from 8 to18 times, although most urologists will take about 12 samples. These are sent to the lab to see if cancer is present.

Though the procedure sounds painful, it may only cause a very brief, uncomfortable sensation because it is done with a special spring-loaded biopsy instrument. The device inserts and removes the needles in a fraction of a second. Most doctors who do the biopsy will numb the area first with local anesthetic. You might want to ask your doctor if he or she plans to do this.

Some doctors will do the biopsy through the perineum, the skin between the rectum and the scrotum. The doctor will place his or her finger in your rectum to feel the prostate and then insert the biopsy needle through a small incision in the skin of the perineum. The doctor will also use a local anesthetic to numb the area.

The biopsy itself takes about 15 minutes and is usually done in the doctor's office. You will likely be given antibiotics to take before the biopsy and for a day or 2 after to reduce the risk of infection.

For a few days after the procedure, you may feel some soreness in the area and will likely notice blood in your urine. You may also have some light bleeding from your rectum. Many men also see some blood in their semen, which can last for several weeks after the biopsy.

Your biopsy samples will be sent to a pathology lab. There, a pathologist (a doctor who specializes in diagnosing disease in tissue samples) will see if there are cancer cells in your biopsy by looking at the samples under the microscope. If cancer is present, the pathologist will also assign it a grade (see below). Getting the results usually takes at least 1 to 3 days, but it can take longer.

Even with many samples, biopsies can still sometimes miss a cancer if none of the biopsy needles pass through it. This is known as a "false negative" result. If your doctor still strongly suspects prostate cancer (due to a very high PSA level, for example) a repeat biopsy may be needed to help be sure.

Grading the prostate cancer

Almost all pathologists grade prostate cancers according to the Gleason system. This system assigns a Gleason grade, using numbers from 1 to 5 based on how much the cells in the cancerous tissue look like normal prostate tissue.

• If the cancerous tissue looks much like normal prostate tissue, a grade of 1 is assigned.

• If the cancer lacks these normal features and its cells seem to be spread haphazardly through the prostate, it is called a grade 5 tumor.

• Grades 2 through 4 have features in between these extremes.

Because prostate cancers often have areas with different grades, a grade is assigned to the 2 areas that make up most of the cancer. These 2 grades are added together to yield the Gleason score (also called the Gleason sum) between 2 and 10.

• Cancers with Gleason scores of 2 to 4 are sometimes called well-differentiated or low-grade.

• Cancers with Gleason scores of 5 to 7 may be called moderately-differentiated or intermediate-grade.

• Cancers with Gleason scores of 8 to 10 may be called poorly-differentiated or high-grade.

The higher your Gleason score, the more likely it is that your cancer will grow and spread quickly.

Other elements of a biopsy report

The pathologist's report contains the grade of the cancer (if it is present) but it also often contains other pieces of information that may give a better idea of the scope of the cancer. These can include:

• the number of biopsy core samples that contain cancer (for example, "7 out of 12")
• the percentage of cancer in each of the cores
• whether the cancer is on one side (left or right) of the prostate or both sides (bilateral)

Suspicious results

Sometimes when the pathologist looks at the prostate cells under the microscope, they don't look cancerous, but they're not quite normal, either. These results are often reported as suspicious. They generally fall into 2 categories -- either prostatic intraepithelial neoplasia (PIN) or atypical small acinar proliferation (ASAP).

In PIN, there are changes in how the prostate cells look under the microscope, but the abnormal cells don't look like they've grown into other parts of the prostate (like cancer cells would). PIN is often divided into low-grade and-high grade. Many men begin to develop low-grade PIN at an early age but do not necessarily develop prostate cancer. The importance of low-grade PIN in relation to prostate cancer is still unclear.

If high-grade PIN is found on a biopsy, there is about a 20% chance that cancer may already be present somewhere else in the prostate gland. This is why doctors often watch men with high-grade PIN carefully and may advise a repeat prostate biopsy, especially if the original biopsy did not take samples from all parts of the prostate.

Another finding that is sometimes reported on a prostate biopsy is atypical small acinar proliferation (ASAP), which is sometimes just called atypia. In ASAP, the cells look like they might be cancerous when viewed under the microscope, but there are too few of them to be sure. If ASAP is found, there's about a 40% to 50% chance that cancer is also present in the prostate, which is why many doctors recommend getting a repeat biopsy within a few months.

Last Medical Review: 08/25/2008
Last Revised: 05/13/2009