The significance of modified Gleason grading of prostatic carcinoma in biopsy and radical prostatectomy specimens

At an International Society of Urological Pathology consensus conference in 2005, the Gleason grading system for prostatic carcinoma underwent its first major revision. Gleason pattern 4 now includes most cribriform patterns and also fused and poorly formed glands. Our aims were to compare the grade distributions and assess the agreement between biopsy and radical prostatectomy specimens for the modified and conventional Gleason grading. More than 3,000 radical prostatectomy (RP), needle biopsies (NB) and transurethral resection specimens were assigned modified Gleason score (GS). In NB, modified GS 3 + 3 = 6 and 3 + 4 = 7a were almost equally common, while in RP, 3 + 4 = 7a was most common followed by 4 + 3 = 7b. After application of the modified GS on NB, a substantial shift in GS distribution occurred: The proportion of GS 6 and 7 were 48 and 26%, respectively, with conventional Gleason grading as compared to 22 and 68%, respectively, with modified grading. In 368 men, the agreement between NB and RP with a modified GS 6, 7a, 7b and 8-10 in NB was 28, 88, 68 and 64-100%, respectively. The overall agreement improved from 58 to 72% (p < 0.001) compared to conventional GS. The higher agreement with modified Gleason grading may facilitate therapeutic decisions.