Aims: To investigate how the biopsy Gleason score (GS) and the clinical risk classification are changed by the reporting rules.
Methods: A total of 565 prostate biopsy specimens were reassessed. Each Gleason pattern, 1 to 5, was interpreted according to the diagram of modified Gleason grading system proposed by the International Society of Urological Pathology (ISUP). We assigned the GS for each case by the previous reporting rules in our institute (OLD rules), applying the overall-scoring, and ignoring a pattern occupying less than 5% and the tertiary pattern. We also assigned the GS according to the NEW rules, applying the highest-core scoring and reflecting a pattern occupying less than 5% and the tertiary pattern.
Results: GS upgrading by the NEW rules was observed in 195 (35%) patients. Of these, 179 (92%) patients were upgraded only by applying the highest-core scoring. Of 198 patients with GS 6 by the OLD rules, 22 (11%) were upgraded to GS 3+4. Of 172 patients with GS 3+4 by the OLD rules, 59 (34%) and 28 (16%) were upgraded to GS 4+3 and ¡Ý8. Of 108 patients with GS 4+3 by the OLD rules, 63 (58%) were upgraded to GS ¡Ý8. As a result, the distribution of D¡¯Amico¡¯s clinical risk classification (low, intermediate, and high risk) was changed from 26%, 43%, and 31% to 23%, 35%, and 41%, respectively.
Conclusions: Clinicians should be aware that the reporting rules, especially the highest-core scoring, contributes to a significant upward shift of the biopsy GS and risk classification.