Diagnosis
How Is Prostate Cancer Diagnosed?
If certain symptoms or the results of early detection tests have raised the possibility of prostate cancer, your doctor will use other tests to decide whether the disease is present.
The Prostate Biopsy
A biopsy is a surgical procedure in which a sample of tissue is removed for examination under a microscope. A core needle biopsy is the main method used to diagnose prostate cancer. Under transrectal ultrasound guidance a doctor inserts a narrow needle through the wall of the rectum into the area of the prostate gland that appears abnormal or suspicious. The needle then removes a cylinder of tissue, usually about 1/2 inch long and 1/16 inch across, which is sent to the laboratory to see if cancer is present.
The procedure is usually done in the doctor's office and takes about half an hour. Though the procedure sounds painful, it typically causes little discomfort because a special instrument called a biopsy gun inserts and removes the needle in a fraction of a second. Several biopsy samples are often taken from different areas of the prostate. Usually six samples are taken (upper, mid, and lower areas of the left and right sides) to get a representative sample of the gland and tell how much of the gland is affected by the cancer. In some cases, as many as eighteen samples may be taken.
Grading the Prostate Cancer
If cancer is found in a prostate biopsy specimen, it will be graded in order to estimate how aggressive it is likely to be (that is how fast it is likely to grow and spread). Grading is done by the pathologist examining the tissue sample taken during the prostate biopsy. Prostate cancers are graded according to how closely they look like normal prostate tissue when viewed under a microscope. The most commonly used prostate cancer grading system is called the Gleason system.
This system assigns a Gleason grade ranging from 1 through 5 based on how much the arrangement of the cancer cells mimics the way normal prostate cells form glands. If the cancer cell clusters resemble the small, regular, evenly spaced glands of normal prostate tissue, a grade of 1 is assigned. If the cancer lacks these features and its cells seem to spread haphazardly through the prostate, it is a grade 5 tumor. Grades 2 through 4 have intermediate features.
Because prostate cancers often have areas with different grades, a grade is assigned to the two areas that make up most of the cancer. These two grades are added together to yield a Gleason score (also called the Gleason sum) between 2 and 10. Scores of 2 through 4 are often grouped together as low, 5 and 6 are called intermediate, and scores of 7 to 10 are considered high. The higher the score, the more likely that the cancer will grow and spread rapidly, and the worse the patient's prognosis (outlook for cure or long-term survival).
Cancers with a high Gleason score are more likely to have already spread beyond the prostate gland at the time they are found. For this reason, the Gleason score (considered together with the blood PSA level and DRE findings) is useful in considering treatment options and selecting additional tests to be done before choosing a treatment.
Source: AMERICAN CANCER SOCIETY
