Objective: To explore the impact of the 2005 International Association of Urological Pathology (ISUP) Gleason score (GS) system on prostatic carcinoma grading.
Methods: Using the 1977 revision and ISUP version of GS system, 112 needle biopsies, 18 transurethral resections of the prostate and 55 radical prostatectomies were scored. The proportion of grading discrepancy was observed and compared between the two versions of GS.
Results: Gleason scores of 3+3, 3+4 and 4+3 accounted for 47.0% (87/185), 11.4% (21/185) and 17.3% (32/185) in the modified system, and accounted for 25.9% (48/185), 21.6% (40/185) and 27.6 % (51/185) in ISUP system, respectively. The percentages of primary grade by modified vs. ISUP system were 62.7% (116/185) vs.50.8% (94/185) for grade 3, and 31.4% (58/185) vs. 41.6% (77/185) for grade 4. The percentages of secondary grade by modified vs. ISUP system were 65.9% (122/185) vs. 54.6% (101/185) for grade 3, and 21.1% (39/185) vs. 31.4% (58/185) for grade 4.
Conclusions: ISUP system is different from the modified system. Compared with the modified system, the proportion scored by ISUP system tends to decline for GS 3+3 but increase for GS 3+4 and 4+3.