Gleason Grading of Prostatic Carcinoma

Correlation Between Gleason Score of Carcinoma in
Core Biopsies and Subsequent Prostatectomy Specimens

There have been several studies correlating Gleason score of carcinoma in core biopsies and subsequent radical prostatectomy specimens. Exact correlation between biopsy and prostatectomy Gleason scores has been found in 28.2-67.9% (pooled data 44.5%). The biopsies underestimated (undergraded) prostatectomy scores in 24.5-60.0% (pooled data 45.0%) and overestimated prostatectomy scores in 5.2-32.2% (pooled data 10.4%). The subsequent prostatectomy grade has been predicted by biopsy grade within +/- one Gleason score in as many as 74-94.6% of cases. In general, adverse findings (Gleason scores 7-10) on core biopsy accurately predict adverse findings in the radical prostatectomy specimen whereas favorable findings (Gleason scores 2-6) on core biopsy do not necessarily predict favorable findings in the radical prostatectomy specimen. These correlations are affected by both pathology grading error and sampling error.

The most common pathology grading error is seen when pathologists undergrade Gleason score 5-6, assigning a score of 2-4 (See "Overdiagnosis of Gleason score 2-4"). Carcinomas with histology "borderline" between Gleason patterns are another source of pathology grading error (See "Borderline Histology"). In the latter instance particularly, there will always be considerable problems with interobserver, and possibly even intraobserver, variability.

The most common sampling error is when there is a higher grade component present within the radical prostatectomy specimen which was not sampled on needle biopsy. A typical example occurs when a needle biopsy tumor is graded as Gleason score 3+3=6, but in the radical prostatectomy specimen there is unsampled Gleason pattern 4, which results in a prostatectomy grade of Gleason 3+4=7.