Accurate Gleason grading of prostatic adenocarcinoma in prostate needle biopsies by general pathologists.

Abstract

Gleason grading of prostatic adenocarcinoma in core needle biopsies is important for predicting prognosis and selecting appropriate therapy. Previous studies have shown that Gleason scores assigned by general pathologists have a low correlation with those assigned by urologic pathologists, and that general pathologists tend to undergrade prostate carcinoma. To determine if the performance of general pathologists grading prostate needle biopsies has changed over time. Four hundred sixteen prostate biopsies from men treated at a single community-based institution between 1987 and 2000 were reviewed by one urologic pathologist (A.A.R.). The correlation between the original Gleason score and the reviewer's score was determined over time. Cases were divided into those performed and originally interpreted in the first half of the study (1987-1996) and those performed and originally interpreted in the second half (1996-2000). Overall concordance for exact Gleason score was 59% (244/416). The exact concordance of the Gleason score assigned by the original pathologist and the reviewer during the first half of the study was 51%, whereas in the second half of the study the concordance was significantly greater (66.3%, P =.002). However, when grouped into score categories of 6 or less, 7, and 8 or greater, there was no significant difference in the exact concordance between the first half of the study (78.3%) and the second half (78.4%). Fifty-five percent of the cases in which there was discordance were graded as 7 by the reference pathologist and 6 or less by the original pathologist. There was no correlation between concordance in Gleason score and the percentage of tissue involved by carcinoma. The concordance between general pathologists' Gleason grading and that of a reference pathologist in this study is much higher than that in previously reported studies. Although exact concordance has significantly improved over time, concordance by clinically significant groups has remained high throughout the study, is dominated by the difference between Gleason score 7 and 6 or less, and is unrelated to the size of the tumor focus.