In this Q and A from the Prostate Bulletin, Dr. Jonathan Epstein, The Reinhard Professor of Urologic Pathology at Johns Hopkins, talks about the intricacies of prostate biopsy.
Q. Is it possible that a 12-core biopsy can miss a prostate cancer?
Dr. Epstein. Most of the time, good sampling of the prostate means taking 10, 12, or 14 or more cores. Even so, there is potentially a high likelihood of biopsy missing cancer. This depends on where the cancer is located, how big it is, and how the biopsy is performed.
You must understand that it is not just the number of cores that is important, but where the cores are sampled within the prostate. The urologist needs to perform a good sampling of the prostate, taking in the peripheral zone (located next to the rectum, contains most of the glands in the prostate, and is the main site where cancer develops), and making sure not to go too deeply into the gland and overshoot the target areas. That can greatly minimize the risk of missing a cancer. Even so, biopsies are still not perfect, and about 15 to 20 percent of biopsies still miss the cancer.
Q. If the biopsy comes back clean but you still suspect cancer, when should a biopsy be performed again?
Dr. Epstein. This will all depend on how suspicious the urologist is before the biopsy is performed. For example, if there is a very suspicious nodule on rectal exam and the biopsy comes back negative, a repeat biopsy is generally recommended. Then, too, if the PSA is over 10 ng/ml and the biopsy comes back benign, you want to do a repeat biopsy. If there is a rapid rise in PSA shortly after the original biopsy comes back benign, this would also warrant a repeat biopsy.
If there is something very suspicious clinically and the first biopsy is negative, I recommend waiting a few months, but no more than 90 days, before performing the next biopsy. This allows the patient’s memory of the discomfort caused by the biopsy to fade before doing the repeat test.
Q. How difficult is it render a definitive diagnosis after reviewing a prostate biopsy slide?
Dr. Epstein. Looking at and diagnosing limited prostate cancer on biopsy is one of the most difficult diagnoses in pathology, for several reasons. For starters, prostate cancer is often very tiny on a needle biopsy. While some other cancers in the body are obvious in terms of their malignancy and how they appear under the microscope, the findings of malignant prostate cancer tend to be extremely subtle. Put these factors together and you can end up with problems interpreting the slides, with both under-diagnosis and over-diagnosis as possible outcomes.
