Comparison between Gleason Score of Prostatic Biopsy and Radical Prostatectomy Specimens

The present study was undertaken to compare the gleason score and histologic grade of needle biopsy specimens to those of radical prostatectomy(RP) specimen to examine how accurately biopsy specimens reflect the corresponding excised specimens. In this comparative-descriptive study, gleason scoring was made on the needle biopsy specimens from 57 patients with prostate cancer and then on the RP specimens from the same patients, who underwent radical prostatectomy between midyear of 1998 to midyear of 2003 in two main urological hospitals of Tehran. The gleason scores of the two sets of matched specimens were compared. Then, the specimens were grouped into four main histologic grades (well: 2-4, moderate: 5-6, moderately-poor: 7 and poor: 8-10) and then were compared again. Interobserver reproducibility between the two pathologists of two centers were examined. The most common gleason score by needle biopsy and prostatectomy was 6 and 7 respectively. 43.86% of all patients had no change in score assignment, while 21.05% were overgraded and 35.09% undergraded by needle biopsy. When grouped into four histologic grades, the correlation improved, with 56.14% of patients remaining in the same group after RP, 12.2% overgraded and 31.58% undergraded. The most common histologic grade by both needle biopsy and RP was moderately differentiated. 72.73% of poorly differentiated cancer category showed the same grade after surgery and most undergrading was in the well differentiated group(50%). Positive predictive values(PPV) were almost 50% for each well, moderately and moderately-poor differentiated groups, but 72.8% for poorly differentiated tumors. Kappa value was used for the evaluation of interobserver reproducibility and there was relatively good overall agreement(kappa: 0.371, Pv=0.000). A high gleason score on needle biopsy usually indicates a poorly differentiated tumor on RP specimens however, well differentiated tumors on needle biopsy does not correlate with final pathology grade in the majority of cases.