Virchows Archiv | 2021
2019 Gleason grading recommendations from ISUP and GUPS: broadly concordant but with significant differences
Abstract
Despite all the advances in prostate cancer treatment, Gleason grading remains the most powerful prognostic indicator in prostate needle biopsies. This grading system has undergone several modifications reflecting changing clinical practice. These changes were based on expert consensus at meetings organised by the International Society of Urological Pathology (ISUP) in 2005 and 2014 [1, 2]. However, in 2019, two consensus documents were independently published by ISUP and the Genitourinary Pathology Society (GUPS) [3, 4]. While generally aligned, some of the recommendations are contradictory and hence could be confusing for practicing pathologists. We highlight some clinically significant issues raised by these conflicting guidelines and the need for a more unified consensus. The Gleason grading system has evolved with time. The first major change was instituted by Dr Gleason’s group as the original system involved addition of scores for the primary pattern, the secondary pattern and the clinical stage, resulting in a scale ranging from 3 to 15 [5]. The clinical stage was subsequently dropped, resulting in the now familiar histological Gleason scores (GS) ranging from 2 to 10. Changes in clinical and pathology practice, including the use of basal cell markers to define invasive features, prompted further modifications of the grading system following consensus conferences organised by ISUP in 2005 and 2014 [1, 2]. The 2005 consensus meeting resulted in major changes to the definition of the individual Gleason grade patterns, as well as to the rules for GS reporting [1]. In comparison, the changes proposed in 2014 were relatively minor [2]. The changes recommended in 2005 and 2014 were based on international consensus and were adopted by the WHO. In contrast, the 2019 recommendations of ISUP and GUPS were independently developed [3, 4]. Both groups agree onmany of the major changes suggested in these position papers. There is consensus that a “tertiary” or “minor high-grade” pattern component in radical prostatectomy specimens should be included in the GS as the secondary grade, if it accounts for > 5% of the tumour. There is also agreement that a single GS should be reported for multiple cores from a single MRI-targeted lesion. Both groups recommend reporting the percentage of Gleason pattern 4 in biopsies with GS 7 tumours, but neither could achieve consensus whether this should be a required data element in radical prostatectomies. Both ISUP and GUPS recommend reporting the presence/absence of cribriform pattern 4 in biopsies and radical prostatectomies. There are however some differences that could significantly impact radical prostatectomy reporting. ISUP recommends continuing with the traditional approach of excluding a minor (< 5%) higher grade component in a radical prostatectomy specimen from the GS. Thus, tumours that are predominantly pattern 3 with < 5% pattern 4 or predominantly pattern 4 with < 5% pattern 5 would be reported as GS 6withminor pattern 4 and GS 8 with minor pattern 5, respectively. In contrast, GUPS restricts the term “minor tertiary” only to the setting of GS 7 (3 + 4 or 4 + 3) tumours with a < 5% component of pattern 5. Thus, GUPS would recommend reporting tumours that are predominantly pattern 3 with < 5% pattern 4 or predominantly pattern 4 with < 5% pattern 5 as GS 3 + 4 = 7 (< 5% pattern 4) and 4 + 5 = 9, respectively. These conflicting recommendations could result in significant variation in the reporting of tumour grade and stage in radical prostatectomy specimens. An organ confined predominantly pattern 4 * Murali Varma [email protected]