Utility of Reporting the Percentage of High-grade Prostate Cancer.

Gleason score has long been considered the most powerful tissue-based predictor of outcome for prostate cancer. One of the strengths of this system is that it factors in the multiple grades that are often present in a single tumor. However, there is growing awareness of the limitations of Gleason grading. Specifically, few of the original Gleason criteria are currently used and cancers tend to aggregate in the middle of the grade range. Furthermore, it is unclear how cases with multiple Gleason patterns and with different Gleason scores for different biopsy cores should be reported. The International Society of Urological Pathology (ISUP) has recently addressed a number of these issues. In 2005, several modifications of pattern interpretation were made and rules for reporting of biopsies were modified to include the highest grade in the score, even when this was <5%. In 2014, further changes were proposed, focusing on the reporting of cribriform and glomeruloid architecture and the diagnostic criteria for poorly formed glands [1]. Furthermore, it was decided to group Gleason scores into five grade groups, now known as ISUP grades. Emerging issues were also discussed, such as reporting of the percentage Gleason pattern 4 present in biopsy cores. In the upcoming fourth edition of the World Health Organization classification, due for publication in 2016, reporting of grade groups will be recommended, as well as reporting of the percentage of Gleason pattern 4 for Gleason score 7 tumors. The reporting of percentage Gleason 4 tumor tissue has the advantage that this highlights if a cancer is at the lower or higher end of a grade. This is particularly significant, as Sauter et al demonstrate in this issue of European Urology that there is a biological continuumwithin Gleason score 3 + 4 = 7 and