Prostate Cancer Testing & Diagnosis

• Digital rectal exam: Your doctor inserts a lubricated, gloved finger into the rectum and feels your prostate through the rectal wall. Your prostate is checked for hard or lumpy areas.
• Blood test for prostate-specific antigen (PSA): A lab checks the level of PSA in your blood sample. The prostate makes PSA. A high PSA level is commonly caused by BPH or prostatitis (inflammation of the prostate). Prostate cancer may also cause a high PSA level. See the NCI fact sheet The Prostate-Specific Antigen (PSA) Test: Questions and Answers.

The digital rectal exam and PSA test are being studied in clinical trials to learn whether finding prostate cancer early can lower the number of deaths from this disease.

The digital rectal exam and PSA test can detect a problem in the prostate. However, they can’t show whether the problem is cancer or a less serious condition. If you have abnormal test results, your doctor may suggest other tests to make a diagnosis. For example, your visit may include other lab tests, such as a urine test to check for blood or infection. Your doctor may order other procedures:

• Transrectal ultrasound: The doctor inserts a probe into the rectum to check your prostate for abnormal areas. The probe sends out sound waves that people cannot hear (ultrasound). The waves bounce off the prostate. A computer uses the echoes to create a picture called a sonogram.
• Transrectal biopsy: A biopsy is the removal of tissue to look for cancer cells. It’s the only sure way to diagnose prostate cancer. The doctor inserts needles through the rectum into the prostate. The doctor removes small tissue samples (called cores) from many areas of the prostate. Transrectal ultrasound is usually used to guide the insertion of the needles. A pathologist checks the tissue samples for cancer cells.

If Cancer Is Found

If cancer cells are found, the pathologist studies tissue samples from the prostate under a microscope to report the grade of the tumor. The grade tells how much the tumor tissue differs from normal prostate tissue. It suggests how fast the tumor is likely to grow.

Tumors with higher grades tend to grow faster than those with lower grades. They are also more likely to spread. Doctors use tumor grade along with your age and other factors to suggest treatment options.

One system of grading is with the Gleason score. Gleason scores range from 2 to 10. To come up with the Gleason score, the pathologist uses a microscope to look at the patterns of cells in the prostate tissue. The most common pattern is given a grade of 1 (most like normal cells) to 5 (most abnormal). If there is a second most common pattern, the pathologist gives it a grade of 1 to 5, and adds the two most common grades together to make the Gleason score. If only one pattern is seen, the pathologist counts it twice. For example, 5 + 5 = 10. A high Gleason score (such as 10) means a high-grade prostate tumor. High-grade tumors are more likely than low-grade tumors to grow quickly and spread.

Another system of grading prostate cancer uses grades 1 through 4 (G1 to G4). G4 is more likely than G1, G2, or G3 to grow quickly and spread. Read more in the Staging Section.