I always advise newly diagnosed men to get a second opinion on their biopsies from a very experienced person.  That’s because Gleason scores are notoriously inaccurate.  For example, dear husband’s biopsy slides were interpeted by three different pathologists and he was assigned three different Gleason scores.  (First biopsy ordered by urologist, second done by hospital pathologist before surgery and finally, evaluation of the removed tissue itself.)  

I thought the variation in Gleason scores was due in part to the ineptitude of the pathologists. But it turns out that interpreting prostate cancer slides is more of an art than a science.  Here’s an explanation I got from a Johns Hopkins Health Alert bulletin, which presents a discussion with Dr. Jonathan Epstein of JH, a reknowned expert on PC biopsies:

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.